When functionalities of html attributes and css styles overlap - html

1) If inside CSS file we specify the following style:
td
{ text-align:center; }
While in a Html file we have
<td align=”right” … >
then value set in CSS file will take precedence over an inline html attribute and thus elements contained inside <td> cell will be aligned to the center.
a) Is same true for all html attributes? Meaning if a CSS rule and an html attribute functionalities overlap , will the CSS rule always take precedence?
BTW – I know we should usually prefer using CSS rules vs html attributes
thanx

Which set of definitions, HTML attributes or CSS properties, take precedence?
The textbook answer:
CSS properties take precedence over HTML attributes. If both are specified, HTML attributes will be displayed in browsers without CSS support but won't have any effect in browsers with CSS support.
(Reference: http://www.hwg.org/resources/faqs/cssFAQ.html)
The real-world answer:
It depends, if you want to be certain for a specific attribute or set of attributes, you will have to create a unit test and apply those tests to the specific browser(s) that you want to verify for compliance with the "textbook" answer, or compliance to your specification for the specific project you are working on.
You already imply that you know certain HTML attributes are deprecated, so I will not belabor that point here.

Related

How to apply style to HTML subdocuments? [duplicate]

This question already has answers here:
How to apply CSS to iframe?
(28 answers)
Closed 6 years ago.
I tend to apply my own custom CSS documents to certain sites, since I prefer dark backgrounds with light text as opposed to the vice-versa standard, and very few sites have a "dark mode" or otherwise cater to that preference, this site itself being an excellent example.
However, I was recently stricken by something odd - an entire HTML document nested inside of another one. (I now understand this is achieved via use of an <iframe> and so it's nearly impossible to style without JS or something) I can only apply the custom stylesheet to the parent document, though.
So, long story short, I'm wondering what sort of selectors I would have to use to target elements of the nested document only - for example, selecting the <body> of the nested document. Would I refer to a body in a html in a !DOCTYPE that is also in a body? What about recursively nested documents?
Whether this nesting thing is poor practice or not does not immediately concern me -- there seems to be a valid use case for it and, regardless, I'm not building the site. What I DO care about is how to add styles to it externally.
Assuming you literally have a document that has been 'injected' into another document, you would simply target it with the expected identifiers:
To target elements unique to the sub-document:
body body [element] {
}
To target elements that exist within both documents, you would just use the standard:
[element] {
}
The above would apply the style to any desired element that is contained within either document.
Please be aware that you cannot style an iframe inside a document with CSS -- you'd either have to find a way to manipulate the iframe's CSS itself, or use JavaScript to target the desired elements with document.getElementById().
Hope this helps! :)

Inline style vs "inline style" . What is the difference? [duplicate]

This question already has answers here:
What's the difference between the HTML width / height attribute and the CSS width / height property on the img element?
(8 answers)
Differences between assigning attribute, style, and class in div
(3 answers)
Closed 7 years ago.
What is the difference between height="50" VS style="height:50px" ?
And height="50" VS style="height:50"?
I am always confused by this.
Presentation-related attributes such as height="50" where the original way to specify presentation details of HTML elements.
However, they have since been deprecated in favour of CSS, via the style, class and id attributes, which give a lot more flexibility that the original attributes (at the very least because CSS can be extended without touching the definition of HTML itself, but of course also because you get the "cascading" part, as well as multiple units, media-queries, and much more).
You should thus generally avoid such attributes in HTML.
The only exception is HTML in e-mail, as many clients support those attributes but not the CSS versions.
Note that you should generally avoid style attributes as well, in favour of separate CSS, and class and/or id attributes. This allows you to completely separate the HTML and CSS, and makes it easier to change the presentation of your page without touching the HTML (or the code that generates it).
Also, in CSS (and thus in style attributes), you must specify units (except for 0), so height: 50 is not valid, you should use height: 50px (or another unit).
Using style attribute you add rich CSS to the element. Some styling can not be added using HTML attributes. For example <div style="background-color: #ff00ff; float: right"> is impossible with plain HTML attributes.

Why to use "class=" when I can use my own tag?

I just wonder why should I use "class=" identificator instead of my own "tag"()?
Class example
<span class="red"> Hello there! (using class)</span>
.red {color: red;}
Tag example
<div id="reddiv">
<red>Hello, there (using own tag)</red>
</div>
#reddiv red {color: red;}
Its much more easier for me to use my own tags, since its faster to write.
Can you please tell me if doing it in first/second way has any negative/possitive sides?
While this may work in most browsers, your HTML then loses context. When an application like a search engine (or screen readers or anything else that looks at the source) parses your document, what is it to make of a tag named 'red' or 'purple' or 'job'? It won't have context, so you'll lose out. HTML uses a set of predefined tags that have meaning, you can venture out of it but you'll lose the advantage of everyone instantly understanding (all or part) of your document.
If this document is part of a data transfer framework and not on the public web, you should look at XML.
There are many advantages of using class.
First of all, with class, we use css styles which gives a lot more configuration options than simple HTML tags.
We give all the styles and formatting at one olace and just call the class everywhere we want to apply those, which in big projects like ERP, makes a big difference in code size.
The css style is more compatible with latest versions of browsers and a lot of old HTML formatting and style tags are deprecated in latest versions of HTML.
HTML tags behave differently under different browsers and different document modes. Where css will give same result everywhere.
The css classes can be applied to all the relevant tags on page at once just by defining it somewhere at the top of page.
You should also not forget that predefined tags have a lot of default properties and your custom tags none. So you would need to define everthing over again for all elements apart from span.
Also, you can have more than one class on an element, so <span class="red bold">Red</span> is possible.
You can remove, change and swap between classes to change dynamical the element style or behavior, what you can't do with tags.
Tag is element that needs class to set it behavior and style.
Custom elements are created using document.registerElement():
var reds = document.registerElement('red');
document.body.appendChild(new reds());

What can ONLY be done with CSS, but NOT be done with normal DOM style attributes?

I want to know what things can be done "ONLY" with CSS , that are not available using dynamically updated style "attributes" using Javascript. So far I know:
Media queries
Pseudo tags
Any more?
Update:
This question was closed but I asked it as I am trying to decide on the technology to use for a project, but one of the options cannot use CSS style sheets, and can only manipulate the style attribute using javascript.
Inline style attributes can only contain property declarations (e.g. width: 10px or color: red). They can't contain any other CSS constructs: not selectors, at-rules (e.g. #import, #media, #font-face), etc. Just property declarations.
However, they play a big role in the cascade: any styles for an element with that attribute take highest precedence (after considering !important of course).
There's actually an entire module devoted to style attributes, by the way, but it's not essential reading for authors.
So, anything that isn't a CSS declaration, is only possible in a stylesheet, not a style attribute. Not sure if that's what you're asking...
Note that media queries and #media rules are not the same thing; media queries can exist in areas outside of stylesheets too, like HTML's media attribute, where they're next most commonly found.
I believe pseudo classes (:hover etc..) and pseudo elements (:after, :before) cannot be added/manipulated via JS (via the style property i mean) because they are not part of the DOM.

Inline <style> tags vs. inline css properties

What is the preferred method for setting CSS properties?
Inline style properties:
<div style="width:20px;height:20px;background-color:#ffcc00;"></div>
Style properties in <style>...</style> tags:
<style>.gold{width:20px;height:20px;background-color:#ffcc00;}</style><div class="gold"></div>
Style rules can be attached using:
External Files
In-page Style Tags
Inline Style Attribute
Generally, I prefer to use linked style sheets because they:
can be cached by browsers for performance; and
are a lot easier to maintain for a development perspective.
However, your question is asking specifically about the style tag versus inline styles. Prefer to use the style tag, in this case, because it:
provides a clear separation of markup from styling;
produces cleaner HTML markup; and
is more efficient with selectors to apply rules to multiple elements on a page improving management as well as making your page size smaller.
Inline elements only affect their respective element.
An important difference between the style tag and the inline attribute is specificity. Specificity determines when one style overrides another. Generally, inline styles have a higher specificity.
Read CSS: Specificity Wars for an entertaining look at this subject.
Here's one aspect that could rule the difference:
If you change an element's style in JavaScript, you are affecting the inline style. If there's already a style there, you overwrite it permanently. But, if the style were defined in an external sheet or in a <style> tag, then setting the inline one to "" restores the style from that source.
It depends.
The main point is to avoid repeated code.
If the same code need to be re-used 2 times or more, and should be in sync when change, use external style sheet.
If you only use it once, I think inline is ok.
To answer your direct question: neither of these is the preferred method. Use a separate file.
Inline styles should only be used as a last resort, or set by Javascript code. Inline styles have the highest level of specificity, so override your actual stylesheets. This can make them hard to control (you should avoid !important as well for the same reason).
An embedded <style> block is not recommended, because you lose the browser's ability to cache the stylesheet across multiple pages on your site.
So in short, wherever possible, you should put your styles into a separate CSS file.
From a maintainability standpoint, it's much simpler to manage one item in one file, than it is to manage multiple items in possibly multiple files.
Separating your styling will help make your life much easier, especially when job duties are distributed amongst different individuals. Reusability and portability will save you plenty of time down the road.
When using an inline style, that will override any external properties that are set.
I agree with the majority view that external stylesheets are the prefered method.
However, here are some practical exceptions:
Dynamic background images. CSS stylesheets are static files so you need to use an inline style to add a dynamic (from a database, CMS etc...) background-image style.
If an element needs to be hidden when the page loads, using an external stylesheet for this is not practical, since there will always be some delay before the stylesheet is processed and the element will be visible until that happens. style="display: none;" is the best way to achieve this.
If an application is going to give the user fine control over a particular CSS value, e.g. text color, then it may be necessary to add this to inline style elements or in-page <style></style> blocks. E.g. style="color:#{{ page.color }}", or <style> p.themed { color: #{{ page.color }}; }</style>
Whenever is possible is preferable to use class .myclass{} and identifier #myclass{}, so use a dedicated css file or tag <style></style> within an html.
Inline style is good to change css option dynamically with javascript.
There can be different reasons for choosing one way over the other.
If you need to specify css to elements that are generated programmatically (for example modifying css for images of different sizes), it can be more maintainable to use inline css.
If some css is valid only for the current page, you should rather use the script tag than a separate .css file. It is good if the browser doesn't have to do too many http requests.
Otherwise, as stated, it is better to use a separate css file.
You can set CSS using three different ways as mentioned below :-
1.External style sheet
2.Internal style sheet
3.Inline style
Preferred / ideal way of setting the css style is using as external style sheets when the style is applied to many pages.
With an external style sheet, you can change the look of an entire Web site by changing one file.
sample usage can be :-
<head>
<link rel="stylesheet" type="text/css" href="your_css_file_name.css">
</head>
If you want to apply a unique style to a single document then you can use Internal style sheet.
Don't use inline style sheet,as it mixes content with presentation and looses many advantages.
Inline CSS have more precedence than CSS within tag.
There are three ways to add CSS.
Read this article on w3school, very informative.