Can I use this (custom elements, custom attributes) on (for examples) IE 9 with this CSS? Is this valid? What are the negatives?
I want to have more readable code... without divs.
HTML
<row center>
<column number="6">A</column>
</row>
CSS / LESS
row {
background: #444;
display: flex;
&[center] {
justify-content: center;
}
column {
background: #222;
color: #fff;
&[number="6"] {
padding: 1rem;
width: 50%;
}
}
}
The case against custom elements has been made by other answers. As an alternative to this idea, HTML 5 has a number of new elements. These include <article>, <aside>, <figure>, <header>, <nav>, and <section>. Using these elements should make your page layout semantically meaningful, save you from puzzling over a sea of <div> and <span> elements, and be understood by modern browsers.
Making up your own markup language:
May conflict with additional features added to HTML in the future (at least if you tell the browser it is HTML with a Content-Type: text/html HTTP header).
Won't be properly understood by user agents which you can't completely override with CSS (such as screen readers, text browsers and search engines).
Won't be understood by other developers who may have to maintain your code in the future.
Can't use an HTML validator for a cheap, basic QA pass
The W3C is developing a standard call Custom Elements, which allows authors to define their own elements. You can read about it here:
Custom Elements, defining new elements in HTML
Custom Elements allow web developers to define new types of HTML
elements. The spec is one of several new API primitives landing under
the Web Components umbrella, but it's quite possibly the most
important. Web Components don't exist without the features unlocked by
custom elements:
Define new HTML/DOM elements
Create elements that extend from other elements
Logically bundle together custom functionality into a single tag
Extend the API of existing DOM elements
Introduction to Custom Elements
Custom Elements enable developers to create their own custom HTML
tags, let them use those tags in their sites and apps, and enable
easier component reuse.
W3C Custom Elements
Provide a way for Web developers to build their own, fully-featured
DOM elements. Though it was long possible to create DOM elements with
any tag names in HTML, these elements weren't very functional. By
giving Web developers the means to both inform the parser on how to
properly construct an element and to react to lifecycle changes of an
element, the specification eliminates the need for
DOM-as-a-render-view scaffolding that has to exist today in most web
frameworks or libraries.
However, if your goal for today is to write more readable code, then consider sticking with standard HTML elements (or just div and span elements) and using class and id values for descriptions. You can be as descriptive as you like with classes and ids. See my answers here for guidance:
Default settings of unrecognized HTML elements
Is there a standard method for naming classes?
HTML5 ID Attribute Values
My professor asked us to develop a website using pure HTML,
JUST HTML. And it's really hard to design without CSS but I have to follow her instructions.
Anyway, my question is do you consider this code as CSS even if I removed the type="text/css"?
<style>
a {color:white; }
</style>
This maybe a dumb question but thanks for your time to answer it, I just really want to use CSS to make it easier.
Could you suggest anything that would make my coding easier? I just don't want to have repetitive code.
You are having this snippet,
a {
color:white;
}
is an element selector with the color property, whatever you write, i.e, between <style> tag, or style attribute, or stylesheet, all are CSS, if your professor is vintage fan, and is asking you to assign the color to a than you can use the font tag with color attribute with a value of white
<font color="white">Hello</font>
Demo
Note: Please read the box on the Mozilla Developer Network which says
SO DON'T USE IT
And just incase your professor understands, and his mind comes back to 2014... than would like to point out that even using
a {
color: white;
}
will target all the a elements in your document, so make sure you use a class or a specific selector to select particular a element.
Anyway, my question is do you consider this code as CSS even if I removed the type="text/css"?
CSS is CSS, not matter how it is added to the document or labeled.
it's really hard to design without CSS but I have to follow her instructions.
Could you suggest anything that would make my coding easier?
I'd start by clarifying if CSS really is forbidden and, if it is, what the purpose of forbidding it is. I can think of a number of possible reasons:
To prepare you to deal with code written by someone from 1996
To make you focus on the structure and semantics instead of the appearance
The course you are taking is almost two decades out of date
How you deal with the problem depends on which of those is the reason.
If it is the first one, then you need to look at all the obsolete, deprecated (and possibly non-standard too) presentational features of HTML (like <font> and background attributes).
If it is the second one, you just don't worry about how it looks and deal with the structure and the semantics. Let the browser's default stylesheet control the way it looks.
If it is the third one, then you probably have little option but to grit your teeth and bare it or find a better course.
<style>
a {color:white; }
</style>
Yes you write type="text/css" or not it will be considered as css.
The content of a style element is CSS, for most practical purposes (it would hardly make sense to use anything else there, since no other style sheet language is supported by browsers). The attribute type="text/css" does not change this, because the de facto default style sheet language is CSS.
On the other hand, the style element, including its content, is HTML. The content is not defined in HTML but in other specifications. Similar considerations apply to style attributes, as in <a style="color: white">...</a>: the attributes are HTML, and but they contain embedded CSS.
When you are told to use “pure HTML, JUST HTML”, then you are probably expected to refrain from using CSS or JavaScript in any way. On the other hand, you are probably allowed to use images, even though images are not HTML but are used via external references or data: URLs. There is nothing particularly logical in such a requirement.
As suggested in other answers, simply do not try to control the rendering of the page. Worry about the rendering only if it becomes intolerably messy and there is a reasonable way to prevent that in “pure HTML”. For example, don’t try to set link colors (this would in fact be an improvement over the way most web pages deal with links), backgrounds, fonts, etc. But if you use e.g. a data table, consider using , which often makes a table essentially more readable.
Yes, you can:
and too you can put style inline in your body or header
<style>
a{
color: #ffffff;
}
</style>
and so, all your css you can write it in your native .html without use of another .css file
I watched this presentation about object oriented css, but I think I either don't understand it correctly or don't understand the benefits of using OO CSS:
Example HTML:
<div class="border-1 bg-2 color-1 font-1">
</div>
Example CSS:
/* borders */
.border-1 { border: 1px solid red; }
/* backgrounds: */
.bg-2 { background: yellow; }
/* other sections */
I see an advantage in being able to change styles for multiple elements quickly, for instance, being able to switch the color scheme would be very useful.
But actually, you're defining the style/look inside the HTML, or at least a part of it. Of course, it's better than using the style attribute, because you still are able to exchange the styles for a set of groups.
The point is, you are defining the style-groups inside the HTML, but I learned that you should create "logical" groups inside the HTML (e.g. class="nav-item" / class="btn submit-btn") and the CSS completely applies the style and defines which elements belong together from the "stylistic" point of view (e.g. .nav-item, .submit-btn { background: red; }).
Maybe I totally misunderstood the concept. However, I still don't know a good way of constructing my CSS.
CSS isn't object oriented. My suggestion is to forget what you've read about "object oriented CSS" and instead focus on the problems with CSS you're trying to solve. If they are to make CSS easier to write, read and maintain, or to get more features (like CSS variables) I think Less or Sass will suit your need much better.
Using CSS like what's suggested with "object oriented CSS" just leads to terrible, non-semantic and meaningless CSS that in the long run isn't any easier to maintain than "ordinary" CSS. Both id and class should have semantic and meaningful names, so using a framework that allows you to write semantic CSS (that describes intent instead of presentation) is in my humble opinion much better.
This is more of a "name dropping", that an actual method.
The code that you have shown is often derogatory called "enterprise css", there is no excuse for it.
More over, having multiple classes on elements actually hurts performance.
I advice you to adhere to Mozilla's guidelines when making your CSS, which works same for other browsers, too.
And make dedicated .css file with hacks for IE6, 7 and 8.
The idea is that you reuse the same css classes on many elements. This both saves on writing css and on maintaining css. so instead of defining .create-button .cancel-button .create-and-new button you would just have a .button that defines padding, size, background, color, line-height, font-size, font-family and font-weight. And some really small classes for the different button styles like to change the color or font-size
a proper oocss project I often still use can be found here: https://github.com/stubbornella/oocss/wiki
but yes you should have a look at less, it combines the easy of reusing the same css properties on multiple elements with proper class names.
"Object-oriented CSS" is really just a design pattern for how to get most out of your CSS and is basicly the same approach Jonathan Snooks calls SMACSS.
Whether you call it OOCSS or SMACSS, the key to the approach is that you create generic UI elements like the nav abstraction. These UI elements can then be enhanced with more specific features by adding extra classes to the element and/or a container element. Or, as an alternative, you can add your own custom CSS rules using the element's ID or semantic classes.
Further reading :
An Introduction To Object Oriented CSS (OOCSS)
OOCSS + Sass = The best way to CSS
Lots of websites use class names like floatleft, clearfloat, alignright, small, center etc that describe the style that is attached to the class. This seems to make sense so when writing new content you can easily wrap (for example) <div class="clearfloat">...</div> around your element to make it behave the way you want.
My question is, doesn't this style of naming classes go against the idea of separating content from presentation? Putting class="floatleft" on an element is clearly putting presentation information into the HTML document.
Should class names like this that directly describe the attached style be avoided, and if so what alternative is there?
To clarify, this isn't just a question of what to name classes. For example a semantically accurate document might look something like:
<div class="foo">Some info about foo</div>
...
<div class="bar">Info about unrelated topic bar</div>
...
<div class="foobar">Another unrelated topic</div>
Say all these divs need to clear floats, the css would look something like:
div.foo, div.bar, div.foobar {
clear:both;
}
This starts to get ugly as the number of these clearing elements increases - whereas a single class="clearfloat" would serve the same purpose. Is it recommended to group elements based on the attached styles to avoid repetition in the CSS, even if this means presentational information creeps into the HTML?
Update: Thanks for all the answers. The general consensus seems to be to avoid these class names in favour of semantic names, or at least use them sparingly provided they don't hinder maintenance. I think the important thing is that changes in the layout should not require excessive changes to the markup (although a few people said minor changes are okay if it makes overall maintenance easier). Thanks to those who suggested other methods to keep CSS code smaller as well.
It's great until you re-design, and narrow is highlighted yellow, center converts better left-justified, and the image you called floatleft now belongs on the right.
I'll admit to the sin of using floatleft and clear as CSS class names, but it is much easier to maintain your CSS if you choose names that relate to the semantic meaning of the content, like feedback and heroimage.
Presentational class names
The HTML spec is clear on this issue:
There are no additional restrictions
on the tokens authors can use in the
class attribute, but authors are
encouraged to use values that describe
the nature of the content, rather than
values that describe the desired
presentation of the content.
Does clearleft describe the nature of the content? Not really. Eric Meyer made a joke about this a while ago.
Try to find a structural relation between the seemingly unrelated elements
Let's say you have paragraphs about ducks, paragraphs about monkeys and paragraphs about frogs. You want them have a blue background.
<p class="duck"></p>
<p class="monkey"></p>
<p class="frog"></p>
You could add this CSS rule:
p.duck, p.monkey, p.frog {
background-color: blue;
}
But aren't they all animals? Just add another animal token:
<p class="animal duck"></p>
<p class="animal monkey"></p>
<p class="animal frog"></p>
And change the CSS rule to:
p.animal {
background-color: blue;
}
It is hard and it might not always be possible but the important thing is not to give up quickly.
What if you can't?
If you have a lot of elements with absolutely no structural relation between them, that indicates a structural problem with your document. Try to decrease these elements. That said, grouping n CSS selectors on one rule is still better than adding n presentational class tokens in your HTML document.
Style classes should be semantic. This is a great article on semantic web page design (well, I found it really helpful anyway).
EDIT: I just read another article that makes some good points for using things like display: inline-block, display: table etc. instead of floats. That should help avoid those pesky floatleft and clearfix classes. Making them semantic is always up to you though.
The main problem with having classes named floatleft, clear or the like is the fact that changes in the design imply changes in the HTML markup. This should not happen, true separation between content and presentation is achieved only when you can re-use the same markup in multiple designs or even media (think sharing the same HTML between desktop and mobile versions of your site and only switching sylesheets).
Now, for a practical example :). To add on Fredrik's answer, LESSCSS allow you to hide styles declarations/mixins from developers. This way you can protect reusable components in your stylesheets without the danger of having them pop up in your HTML.
Sample markup:
<div class="branding">Company Name</div>
Sample less code:
// example of reusable functions
.noText() {
color: transparent;
text-indent: -9999px;
}
.clear-after() {
&:after {
content: ".";
display: block;
visibility: hidden;
height: 0;
clear: both;
}
}
.branding {
.clear-after();
.noText();
background-image: ...;
}
Of course, for mobile you might just want to have the company name in bold, without any other styling:
.branding {
color: pink;
font-weight: bold;
}
I think it depends on how you are using the styles.
Content should be named accordingly, as the style may change but the content will likely remain the same.
For instance, if you have a div that contains stock info, you should name the div something like div class="stockInfo", so that no matter what the presentation, you can change the styles and the name will not contradict those styles (as opposed to naming the div div class="yellow" and then changing the background-color to red).
However you will have "helper styles" and these should be named for what they do.
For instance, you will likely want to use a <br /> to clear some floats. In this case, it is perfectly reasonable to name it <br class="clear" /> and to give it a style of br {clear:both;}.
Again, most Web sites float their images right or left. To assist with this, you can set <img class="right" src="" /> and <img class="left" src="" /> and then have the styles to match, img.right {float:right;} etc.
So it depends on the usage.
Class names and ids that describe the function is better than using names that describe the styling of the element.
I usually end up not doing it religiously though, because it is in my opinion more convenient to i.e. clear floating elements by using the famous clearfix hack rather than adding clear:both all over the stylesheets.
But I think that LESS and SASS creates interesting opportunities to get the best out of both worlds, because you can have mixins and functions that describes some style and still have semantic correct names by just including whatever 'style' you want.
Instead of having this HTML and CSS
<div class="navigation roundedcorners">...</div>
.roundedcorners {
-moz-border-radius: 5px;
-webkit-border-radius: 5px;
border-radius: 5px;
}
you could use SASS to create this mixin:
=rounded-corners
-moz-border-radius: 5px
-webkit-border-radius: 5px
border-radius: 5px
and include it into your .navigation class like this:
.navigation
+rounded-corners-5px
which would reduce your HTML to this:
<div class="navigation">...</div>
and therefore still get the advantage of having semantic correct names while having a convenient way to share styles between different elements.
Andrew; it's good to give sensible name to an class & id which easy to understand for you & your fellow member's which are working on that project. For me classes small , center , floatleft etc define nothing to me because when you give class center that's indicate that the element on the center but there are other properties also in that class like color, background etc
For example
<div class="wrap">
<div class="center">lorem</div>
</div>
css:
.center{margin:0 auto;}
in this example class center don't clear to me. but we can use them as a helper class.
For example
<div class="wrap">
<div class="panel center narrow">lorem</div>
</div>
css:
.center{margin:0 auto;}
from above example now it clear to me what the role of class center in that panel div
FOR MORE CHECK THESE LINKS :
What's the best way to name IDs and classes in CSS and HTML?
http://www.ronniesan.com/blog/entry.php?title=organizing-your-dom-elements-with-the-proper-ids
http://cssglobe.com/post/3745/my-top-10-most-used-css-class-names
If your question is:
Is it recommended to group elements
based on the attached styles to avoid
repetition in the CSS, even if this
means presentational information
creeps into the HTML?
Then my flat answer would be that in real world, semantic and presentation isn't everything. So my answer would be: it depends.
...depends if bandwidth is important to you... On a site with many visitors per hour, then the classnames could even simply be something like "c11" (yes, I've seen it) instead of meaningful, but looong class names.
...depends also if you perfectly know that when the look and feel will change, then the CODE will change also. (exemple: you redesign a site today in XHTML, but you perfectly know that when you'll re-do the CSS in 2 years, then you'll want the markup to be HTML5, so you will pretty much change the structure anyways...)
...depends also if you're already 3 days late on a delivery. When you're 3 days late, believe me, classnames like "nopadding" starts to appear, as you don't have anymore time to think straight about semantic (neither does your client).
Depends on so many things, I'd say... That's my "real life" point of view of your question.
From what I've seen, developers have the tendency to overload their HTML pages with way too many unnecessary classes and extra markup. These classes not only make the page size bigger (and thus the load time longer), they also crowd up the page and make it difficult to manage and modify at a later time.
Having things like center and float-left might be helpful when you're dealing with display text that was input by a user (such as a post on a forum), but for general markup purposes you're better off just adding text-align: center and float: left to the appropriate classes. This especially helps if you are trying to change the appearance of your site without changing the HTML much. The less you have hardcoded into your template, the easier it is to only have to change around the CSS when modifying your template. That bit alone is worth it to me.
As a general rule of thumb, you really should only give elements classes when it describes what the content is, not where or how it is being displayed. i.e. <span class="movie-information"> instead of <span class="bold">.
The only time I feel that it makes sense to give an element a class when it isn't necessary is if you are concerned with Search Engine Optimization. You should definitely read up on Microformats if you are interested in seeing how adding the right classes can actually help search engines. That being said, adding classes that describe how the page is visually displayed does nothing for the search engines.
The only time I would ever "group" classes is if they are either displaying the same thing, or if they are siblings. It gets really messy in your CSS when you have elements from all over your page defined together. You're much better off grouping your classes in your stylesheet in ways that you will be able to find them later, rather than saving a few lines by combining them.
I think this is where old meets new in web technologies. From times past, it has been difficult to unobtrusively render an outstanding web experience. These class names mostly came in handy when websites were changing webmasters to aid them in understanding the code. It served its cause well but with the new technologies of this day and age, I think this is slowly dying out - infact, it should be dead.
The question we should ask is, "Do we need to create a new class for every new innovative design that could pass as a template?". I do not think so. The markup on a site should do what it is meant for - markup. The class names used in the markup should be descriptive of the content and not its looks. The stylesheets - on the other hand - should be able to select elements on a document based on the information in the markup, and style them.
I want to relate this to the Rails association naming convention. Consider this...
class Post < ActiveRecord::Base
has_one :personifyable
has_many :personifications, :through => :personifyable
has_many :taggables
has_many :tags, :through => taggables
belongs_to :destroyers
end
Obviously, this is not a real model; it is something I am using to drive a point. Consider the case of a deeply nested dependency. These names will grow ridiculous - if they aren't already (i.e. in CSS, <div class='mediumwidth floatright centeredtext graytheme master'></div> or something of the like)
Now consider the case where you have different principles. Different developers and designers may - if not 'most definitely will' - have different reasons for using a specific naming convention. How would this affect refactoring time. I will leave that to your imagination. Also, if your business partner notices a new trend with sites themes that attracts traffic - more technically, assume this business partner has performed some experimental A/B testing and come up with some specs - you don't want to change the contents of the whole stack (ie HTML and CSS and possibly JS pages) to implement this new style.
In conclusion, keep styling hints out of your markup. Unobtrusively interact with the document to style and manipulate it. Sass gives you a fine way of styling a site while having your CSS mock your markup. jQuery is another awesome UJS library. HTML5 gives you methods too that make the markup more flexible and yields more information to CSS and JS.
I don't think adding a descriptive class name to your document is really a big issue. I find it's easier to work with explicit class names like "floatleft" as opposed to things that are purely semantic or reliant on the cascade. It's usually easier for later developers who don't have the document structure in their heads as well.
You don't want to use them for everything--you wouldn't want to add a class of floatleft to every li in a left-floated menu, but these kind of styles are very good when you need to do a specific thing to one or more elements, and you want to make other developers aware that you did it.
It's like putting in <div class="clear"> or even <div style="clear:both;">: maybe not the prettiest but it sure is obvious what you are doing.
My rule of thumb is: whatever makes you have to think less, do that.
EDIT: As I said in my comment above, this is most true for classes that refer to clearing and floats, i.e., things that are purely presentational, non-semantic, and yet must be referred to in the HTML. I think in this case it is actually preferable to indicate that you are using a purely presentational class, like floatleft, rather than forcing the float to be attached to some semantic element.
I am a developer before a programmer, so for me I use something like a "floatleft" css class as a sort of UtilityMethod.
Meaning, my css class is "floatleft"...and that's all that class does.
so if I say <div class="floatleft"></div> in my mind that is saying "make this div float to the left".
So if that Div also needs a blue background and is my main header it's going to have a different class for that and I end up with <div class="mainheader floatleft"></div>
Doing it this way also avoids issues with refactoring. If I am changing my design later, I will know that "floatleft" ALWAYS floats things left and nothing more.
I think, at the end of the day it is about what works for you. If your class name is descriptive of what it does, that does not really go against the rule of separating markup from styles. Another factor to consider is, are you the sole developer, or part of a team. If you are part of a team, or you know your code will be worked on later by other devs, you should establish, and document the naming conventions used.
I am currently contracting with Down Jones on some very large projects, and we have a rather lengthy document on naming conventions for our classes, including when to use camel-case, or dashes or underscores, as well as specific prefixes on the class name based on the project we work on. It sounds crazy, but when you have a dozen or so front-end devs working on stuff at the same time, it is a life saver!
You are saying something like this:
.red
{
color:red;
}
so in order to use this class:
<ul>
<li class="red">hello</li>
</li>
ALTERNATIVE SOLUTION
ul li
{
color:red;
}
Usage:
<ul>
<li>Hello</li>
</ul>
By this you can actually remove the presentation information from the content.
I personally name them things close to what they will be doing. Say I have a class that is on an image gallery and its a primary most used class it will be something like "gallery" or if I'm setting borders around things that are meant to be more decorative I'll name it "decoborder". I try to keep them semi short and somewhat related what task they provide. I don't like to do things like "small, large, H1underlined" or anything that can mimick another tag or function because that can just get confusing. Beyond that I think you should really name it in whatever way makes the most sense to you.
If the question is only one of naming, then for one specific class...
class="floatleft"
or
class="myClass"
or
class="gibberish"
....changes absolutely nothing. They are only different class names. The programming functions the same.
Either your content & presentation is separated, or it isn't... totally regardless of how you created the names.
For what it's worth, if I remember correctly the class keyword in HTML isn't currently used for anything other than CSS stylesheets. Thus, the example that you provided...
<div class="foo">Some info about foo</div>
...
<div class="bar">Info about unrelated topic bar</div>
...wouldn't really be a way of identifying data. I would suggest either the name or id attribute if you really want to identify data within your HTML tags. (They both have slightly different uses - name is generally used for server-side queries while id can be styled and is generally more versatile. IDs must be unique, but names don't have to be.) You can check further documentation using the W3C HTML specification.
In short - don't worry about tying content to presentation through your tag classes; until they're specifically used for anything else, they will not have any real effect on your raw content. As such, I'd say name your classes whatever you want, as long as it makes sense. Personally, I would err on the side of logical naming versus style-type naming (e.g. class name "editorcomment" instead of class "graybgfloatleft" or something like that), but in the end, your class names aren't going to tie your data to your presentation like an ID or a name would.
Good luck.
I've done both and I have to say nowdays I lean towards using non presentational classnames. I found this nifty framework called OOCSS https://github.com/stubbornella/oocss/wiki which helped me alot when I was creating a new layout for my web application and suited my requirements so well.
It is mostly because the definition of basic classes for spacing, headers and text works so well when you have to deal with alot of content. Because you use the same classes everywhere it helps make the layout better and maintainable.
Offcourse this means a element in your html can look like this: <div class="unit size1of3 lastUnit"> But isnt that what HTML is about? Making sure your information is presented properly.
I disagree on the whole redesign point, be honest, when you have to redesign your website most CSS goes out the door anyways. And, by dividing the CSS into proper classes for spacing/heading/text it becomes less likely to have conflicting css rules that mess stuff up like ul li div{}
Offcourse the classes do not describe the contents, but as CSS does not allow class inheritance and you have to support old technology like IE6...does it really matter? And do classnames like animal and duck really make for better html? Id like to think HTML is for the browser and when the browser renders it, thats for humans.
It depends, sometimes it makes sense just to add a class to let an element float. The problem with the semantic approach is that you will end up ball of mud of css classes. Sure, names like redLink or blackHeader have to be banned but sometimes you will need little helpers like "clear" or "floatLeft".
Read this article of Nicole Sullivan who explain this in deep.
There are two things that I feel get entirely left out of these discussions all too often. The first is WHY you would want to be all semantic or all not. The keywords are Branding and Skinning. Presentational class names may be justifiable if you work on some internal, departmental websites where branding and skinning will never in a million years get funding. On the other hand, customer facing sites, such as car manufacturers and department stores live in a world where every single new product that gets launched results in an entirely new skin for the website. New colors, new layout, new background images and all of this lead by designers who should be able to make the change purely in css so there's no chance they can break any working php (or what-have-you). There are also branded sites, where you have multiple skins, potentially running on the same site simultaneously. On sites with that requirement, you can't have visual changes impact html or you end up breaking every other brand just to update one of them. In these situations, semantic class names are a necessity.
The second thing that often gets left out is how to combat the problem of repeating groups of properties created by semantic class names, as in:
.content-nav {
float: left;
margin-right: 10px;
background-color: #ccc;
}
.content-nav .user-photo {
float: left;
margin-right: 10px;
border: solid 1px #000;
}
.content-nav .user-display-name {
float: left;
margin-right: 10px;
text-decoration: underline;
}
People often point this out as a drawback of semantic names, and I think that that's a valid point. On the other hand I would like to point out that there are tools that can help you keep semantic css DRY, such as LESS and SASS. I did see one other commenter mention this above, but I just thought that this point was worth highlighting.
In creating CSS styles one approach seems to be a fully qualified style such as
#pnlImage div.ipd-imageInfo div.ipd-tags span.ipd-tag
compared to a shorter definition such as
div.ipd-tags span.ipd-tag
which would uniquely identify the style as well. However, if the site is expanded or changed the 2nd style runs the risk of not uniquely identifying the element.
Is there a performance hit from fully qualifying a style, i.e., it is longer? Are there some guidelines/best practice references for style naming?
Thanks
Google (not a search, actually them) seems to think that it does cause a performance hit.
Also, the Mozilla foundation has an article "Writing Efficient CSS for use in the Mozilla UI" that outlines the possible performance pitfalls of CSS selectors in their browser(s), and how to optimize your style rules for their rendering engine. Their article has tons of examples of what's good and what's bad. Please keep in mind this is only relevant to their browsers, though.
There are also some benchmarks publicly available, about CSS selectors affect on rendering speeds:
http://www.stevesouders.com/blog/2009/03/10/performance-impact-of-css-selectors/
http://blog.archive.jpsykes.com/153/more-css-performance-testing-pt-3/
I, however, think this is, for the most part, horse manure. You can effect FAR greater change on your page's loading/rendering speed by using some other simple optimizations. I believe that your sanity, and a well-organized code base should come first. If this were as big of a deal as some make it out to be, we'd all be back using HTML < 4 attributes (bgcolor=, border=, etc) to style our web pages.
Looking up an #id is fast.
Looking up a tag is a bit slower.
Looking up a .class is the slowest.
Starting your selectors with a faster lookup will reduce the number of lookups required for then next part. That is, if I wrote p.myClass, then the browser can very quickly find all the p tags and then it only has to loop through those to check for the class name.
That said, it would rate the maintainability of your CSS file higher than its rendering speed. Blah blah blah premature optimisation blah blah.
You might be interested in David Baron (Mozilla)'s Google Tech talk.
I have a site where another designer used heavily qualified styles and maintenance is a nightmare. (the qualified styles are only one part of that)
Basically, you can't touch or simplify the html structure without it breaking half the styles, and the styles often don't cascade properly to new content additions. If you add new css you in turn have to qualify your new rules heavily or half of them end up overridden by some existing rule because it contains so much specificity.
So from a maintenance standpoint it's not efficient. Also not efficient from a typing standpoint either.
I don't see how a theoretical answer is possible: the answer is implementation-dependent; so I suggest you profile it to be sure.
Is there a performance hit from fully qualifying a style, i.e., it is longer?
Yes, on every dynamic change of the DOM-tree, the CSS-expression has to be rematched against at least some nodes. I doubt this will lead to any noticeable delay, though.
Your stated objective (making the selectors robust against changes to the page structure) is not quite solid: hardcoding intricate details about the site structure into the CSS will just mean that you'll have more statements to maintain and update when the page structure changes.
If it's under your control, stick with simple classes (even if you have more of them) and as few levels as possible (doing some relative sizing of fonts is the only use case where I have used several levels, and even this was somewhat superfluous). It just wastes too cognitive capacity to keep track of the page structure in your head.
Although your question is about the performance, (and I would suggest, measure it..) I would really like to add that you should always try to use the shortest definition possible to identity the correct elements.
The reason is not the file size, but the ability to extend your site without altering the main css.
For example you've got this part in your html site:
<div id="Header">
<h1>Css example</h1>
<h2>Welcome to the css example site</h2>
<p>An example page by davy</p>
</div>
and this is the css:
#Header
{
background-color: #ffeedd;
padding: 1em;
}
#Heading h1
{
font-size: 3em;
color: #333;
}
#Heading h2
{
font-size: 1.5em;
color: #666;
}
#Heading p
{
margin: 0 0.5em 1.5em 1em;
font-size: 1.1em;
color: #999;
}
And later on you'd get to a page where you'd like your header to have a different background.
Had you chosen to use div#Header in you main css file, you'd either have to change the html (which depending on your system might mean creating a different template/masterpage) to add an extra class, or create a more qualified css selector such as body div#Header.
Using the shortest selector you could still use div#Header { background : ... } to change your header. You can either create an extra css file and load that into your header on that page (if allowed) or add a style definition directly to your <head> section. The nice thing about this is your css file does not grow with selectors for each different page, and you can keep clear of classitis.
You could also use it to switch the sizing method of your page (static/fluid) so that one template/masterpage uses the default css, and the other derives from that template/masterpage and just links a css called FluidWitdth90.css to change the template to 90% width fluid layout.