Nullify css rules - html

Okay, this is a gross oversimplification, but I have a javascript application to help people develop webpages. It has its interface superimposed over the page that is being developed, and it all works fine, apart from one thing.
If the div class used in the interface is used by the webpage that is being developed, the interface' embedded stylesheet overrides the properties of the webpage!
This happens on jsfiddle, the embedded css is takes precedence over the external css.
JSfIDDLE
external css:
.color {
color: green;
}
Index.html:
<style>
.color {
color: blue;
}
</style>
<div class="color"> Text to be coloured </div>
When run, the text is blue. If someone could make the text turn green, I think it would demonstrate how to overcome the problem.
Obviously, one way to fix this would be to change the interface classes and rules to something like this:
<style>
.color_interface {
color: blue;
}
</style>
<div class="color_interface"> Text to be coloured </div>
And make them unique, but the project has hundreds of css rules, and I'm just wondering if there's a better way, and a safer way (there's still a small chance someone has a rule "color_interface") to do nullify css rules, so they won't contaminate the page.
I'm thinking the only way to do it is probably a 'reset' stylesheet concerning my rules, setting them all back to their defaults. Is there a way to do this dynamically with jquery, maybe?

What you're witnessing is CSS by design. Specifically, specificity.
If your goal is to release some kind of library that can be used publicly and you want to avoid naming conflicts, I think a fair practice is to simply namespace your selectors, e.g., .starkers-color { color: blue; }. That won't necessarily avoid specificity issues, but it should prevent against having your selectors overridden by implementors.

If you inspect the JSFiddle page you'll see that the reason for it not working is that your inline style definition is placed in the body where it has no effect.
The CSS rules you specify is instead placed as an inline style in the head element.
To your problem:
Again, referring to JSFiddle, would it be possible to load the page in development inside an iframe? This would mean you get the separation you require.

This is because the order of the CSS when rendering. Your include is at the top of the page but your style tags are below that, meaning your style tags will alway take precedence over you include at the top. You could try adding an important to you css includes but this is majorly hacky and could create a whole load of new issues.

Related

css override in same page

I tried to find an answer but nothing...
I have a small application that loads in to other websites inside a div tag. This div has a specific id like -> "myAppHere"
Now, all the html is inside this div, but as I can see my elements are affected by each site own css rules.
Is there a way to cancel all the other sites css rules?
something like:
#myAppHere *{
padding: 0;
margin: 0;
etc....
}
because the above sample code doesn't work well.
You cannot simply add:
#myAppHere * {
...
}
cause general rules are overwritten by more specyfic rules. You didn't say in what way app is loaded in that div(is it inner frame, plain HTML etc.) so it's hard to find a solution.
What you can do(assuming it's just extra HTML added to your #myAppHere element) is to check CSS styles set to each element(using e.g. Firebug) and write your on rules in your CSS file, which are more specyfic.
That's a scary requirement you have there.
You can try adding !important to the css rules, like so:
#myAppHere *{
padding: 0 !important;
margin: 0 !important;
etc....
}
but even this won't override some elements that have a style attribute with !important in the rules, such as when this happens:
<div id="myAppHere">
<div style="margin: 20px !important;">Hello</div>
</div>
You may be able to go into the other website's source with javascript, and strip out all style and class attributes... that's probably the only way to be sure. Something like this, if you're using jquery with your javascript:
$("#myAppHere *").removeAttr("style");
$("#myAppHere *").removeAttr("class");
Careful about removing those class attributes though, because it means that if you want to style it yourself, you won't have any classes to work with. You could add new classes in afterwards with more javascript though.
If you insert a complete HTML document inside a div element, the result has invalid markup in a manner that seriously messes things up. In particular, if the inner document has any style element, it will in practice be taken as applying to the page as a whole.
The solution is to stop doing that (and first consider whether you can legally do such things at all – it would normally constitute copyright violation). Technically, you would need to remove or rewrite much of the content of the document being embedded (there is no simple way to deal with CSS code in them or linked from them, for example), or to use an iframe element (or frame or object element) to embed a page as “autonomous” (so it will be displayed in an independent sub-window).

How to raise css rules priority for an html snippet

I wrote a HTML/CSS snippet that is included in some 3-rd party website.But CSS rules of that website make my snippet look terrible. To keep the snippet's appearance I must use !important keyword, but it's horrible, I have to write this keyword for about 1000 times (besides such a code looks not very nice).I can also use inline CSS instead of external .css file, but it's not a solution too.So, how can I protect my css styles in some elegant way?
The suggestion to use a div with a unique ID is good. However, there is a chance that other rules in the host page's style sheet use !important. Those rules would override yours, even if you use a unique ID.
Short of using an external document in an iframe in the first place (which is not always possible), using !important is the only 100% safe way that I can see.
Your snippet should be included inside an iframe.
It's the usual way these "widgets for 3rd party sites" work.
If you use an iframe, CSS from the parent document can't affect your "HTML/CSS snippet".
You can try enclosing your snippet inside a DIV with a unique id.
Then on your CSS for that snippet's style, include the id selector of the DIV for the items in your stylesheet.
The only way I can think of is to make the selectors more specific in some way. For example,
LI { color: red; }
LI.class { color: blue; }
<li class="class">I will be blue</li>
but you're really at the mercy of the 'rest of the CSS' you don't have control over.
I think your best bet is to put ID's and unique classes on all yoru stuff and spec the heck out of it. This is not great either though becuase you might WANT some of the 'rest of the CSS' to apply.
If you can't go with the iframe method, you'll need to figure out what level of specificity the parent page declarations have and beat that with your style declarations, keeping in mind that they'll still apply if you don't clear them. Otherwise, bring on the "!important"s!!! You may want to look for a clear.css or something as well that does this for you, as many sites offer this.

When to use the !important property in CSS [duplicate]

This question already has answers here:
What are the implications of using "!important" in CSS? [duplicate]
(9 answers)
What does !important mean in CSS?
(5 answers)
Closed 4 years ago.
Consider:
#div p {
color: red !important;
}
...
#div p {
color: blue;
}
I understand how !important works. In this case the div will render red because now it has priority (!important). But I can't still figure out an appropriate situation to use it in. Is there an example where !important saves the day?
This is the real life scenario
Imagine this scenario
You have a global CSS file that sets visual aspects of your site globally.
You (or others) use inline styles on elements themselves which is usually very bad practice.
In this case you could set certain styles in your global CSS file as important, thus overriding inline styles set directly on elements.
Actual real world example?
This kind of scenario usually happens when you don't have total control over your HTML. Think of solutions in SharePoint for instance. You'd like your part to be globally defined (styled), but some inline styles you can't control are present. !important makes such situations easier to deal with.
Other real life scenarios would also include some badly written jQuery plugins that also use inline styles...
I suppose you got the idea by now and can come up with some others as well.
When do you decide to use !important?
I suggest you don't use !important unless you can't do it any other way. Whenever it's possible to avoid it, avoid it. Using lots of !important styles will make maintenance a bit harder, because you break the natural cascading in your stylesheets.
Overwriting the Style Attribute
Say in the example that you are unable to change the HTML source code but only provide a stylesheet. Some thoughtless person has slapped on a style directly on the element (boo!)
div { background-color: green !important }
<div style="background-color:red">
<p>Take that!</p>
</div>
Here, !important can override inline CSS.
This is a real, real life scenario, because it actually happened yesterday:
Z-index in jQuery dialog. Autosuggest list not displayed properly
Alternatives to not using !important in my answer included:
Hunting down in JavaScript/CSS where a certain elusive property was being applied.
Adding the property with JavaScript, which is little better than using !important.
So, a benefit of !important is that it sometimes saves time. If you use it very sparingly like this, it can be a useful tool.
If you're using it just because you don't understand how specificity works, you're doing it wrong.
Another use for !important is when you're writing some kind of external widget type thing, and you want to be sure that your styles will be the ones applied, see:
Appended control's CSS
You generally use !important when you've run out of other ways to increase the specificity of a CSS selector.
So once another CSS rule has already dabbled with Ids, inheritance paths and class names, when you need to override that rule then you need to use 'important'.
!important is somewhat like eval. It isn't a good solution to any problem, and there are very few problems that can't be solved without it.
I have to use !important when I need to overwrite the style of an HTML generated by some JavaScript "plugin" (like advertising, banners, and stuff) that uses the "style" attribute.
So I guess that you can use it when you don't control the CSS.
Strictly speaking you shouldn't need to use !important if you've structured your CSS well and don't have too many degrees of specificity.
The most appropriate time to use !important is when you have one exceptional style that you want to style outside of your site's normal cascade.
Using !important is generally not a good idea in the code itself, but it can be useful in various overrides.
I use Firefox and a dotjs plugin which essentially can run your own custom JS or CSS code on specified websites automatically.
Here's the code for it I use on Twitter that makes the tweet input field always stay on my screen no matter how far I scroll, and for the hyperlinks to always remain the same color.
a, a * {
color: rgb(34, 136, 85) !important;
}
.count-inner {
color: white !important;
}
.timeline-tweet-box {
z-index: 99 !important;
position: fixed !important;
left: 5% !important;
}
Since, thankfully, Twitter developers don't use !important properties much, I can use it to guarantee that the specified styles will be definitely overridden, because without !important they were not overridden sometimes. It really came in handy for me there.
The use of !important is very import in email creation when inline CSS is the correct answer. It is used in conjunction with #media to change the layout when viewing on different platforms. For instance the way the page looks on desktop as compare to smart phones (ie. change the link placement and size. have the whole page fit within a 480px width as apposed to 640px width.
This is a real-world example.
While working with GWT-Bootstrap V2, it will inject some CSS file, which will override my CSS styles. In order to make my properties to be not overridden, I used !important.
I'm using !important to change the style of an element on a SharePoint web part. The JavaScript code that builds the elements on the web part is buried many levels deep in the SharePoint inner-workings.
Attempting to find where the style is applied, and then attempting to modify it seems like a lot of wasted effort to me. Using the !important tag in a custom CSS file is much, much easier.
I am planning to use !important for a third-party widget meant to be embedded in a large number of websites out of my control.
I reached the conclusion !important is the only solution to protect the widget's stylesheet from the host stylesheet (apart from iframe and inline styles, which are equally bad). For instance, WordPress uses:
#left-area ul {
list-style-type: disc;
padding: 0 0 23px 16px;
line-height: 26px;
}
This rule threathens to override any UL in my widget because id's have strong specificity. In that case, systematic use of !important seems to be one of the few solutions.
You use !important to override a css property.
For example, you have a control in ASP.NET and it renders a control with a background blue (in the HTML). You want to change it, and you don't have the source control so you attach a new CSS file and write the same selector and change the color and after it add !important.
Best practices is when you are branding / redesigning SharePoint sites, you use it a lot to override the default styles.

Is there any way to use inline styles to define a:visited link style?

So instead doing it using css:
<style type="text/css">
a:visited {
color: red;
}
</style>
Could it be done using inline code. Something like this doesn't work:
<a href="http://google.com" style='a:visited:color:red'>Google.com</a>
You can't do this, the specification (CSS2 here) covers it briefly here:
Neither pseudo-elements nor pseudo-classes appear in the document source or document tree.
:visited along with the others modifiers are all pseudo-classes, and there was never a standard syntax setup to do what you're trying. Honestly this is the first time I've ever seen it requested, so I don't think it'll be added to the specification anytime soon...sorry that answer sucks, but it is what it is :)
Just to add one motivation to achieve this inline style for the various a href states:
in some page it could appear text with link in one are where the background is different from the overall background.
The main CSS for the "a" gives them one color that is not good on that particular and singular area.
For this reason, to give the user the idea that the link is a link, you need to color that link differently from the others.
For me it worked to set some style="color: #5070BB;" inside the <a href=".." tag, but maybe that neither the a:visited nor the a:hover colors are good for that background and it would be useful to set them inline.
Yes, it is definitely a singular and lonely situation, but that is a real case.
Ciao!
Sure you can....
<a href="https://www.yahoo.com/" target="_blank"style="text-decoration: none; border-bottom: 1px solid pink;color:pink !important;">
some link
</a>
jfiddle
No, that's not how inline styles work. It is in the specification, however browsers don't seem to support it.
No. Pseduoclasses (e.g :first-child, :hover) are used as selectors based on behavior and relation to other DOM elements. Inline styles contain rules. Even if at some point browsers do support this, it'll feel weird.
As far as I know, it isn't supported ... but to add some clarification for the reason for wanting to do this, since it would definitely be the sub-optimal way to do it on a regular web page, the reason would be to use in HTML email, which, except for certain good email clients, does not support regular style sheets, so it's necessary to define all styles inline to ensure good support across email clients (Gmail and Outlook (ugh) come to mind.)
Of course, it's possible to use some other program that lets you import a stylesheet and automatically convert it to inline styles, which is much easier to manage (that's what I do), but you're still using inline styles in the end-analysis.

override definition in css file

I have a css file that defines style for all <p> tags.
like this
p { ......... }
How can I write a <p> in a page where the stylesheet is included that has default styling?
There's no easy way to do this.
There a some common tricks to simulate that behavior though. The best one to use would vary based on how complex the overridden region is, and how often you want to do this.
Method 1 (for simple overrides):
Add an extra class definition in the statement similar to the one where you clear the default styling (such as is discussed at http://www.wordpress.darfuria.com/blog/clear-css-defaults). You might have to arrange the declarations carefully to prevent the 'normal' style from taking precedence.
.override {/*Your default style overrides, color: white;
margin: 0; background:none; etc */}
<p class="override">foo</p>
Method 2 (clunky, but good for complex regions):
Use an iframe to pull the whole region from a separate .html file hosted elsewhere on your site. The content inside iframes respects the CSS of the page inside the frame, and generally ignores the CSS from the surrounding page.
Method 3 (good for one-shot overrides):
Use inline styles, as others have described here.
Edit:
Not Really a Method, But Probably The Most Correct Way
Also probably not what you want to hear
Re-think your how you've arranged your classes.
For example:
If the overridden <p> is special in some way, it probably deserves it's own class that describes what it's purpose is. <p class='override'> doesn't help people who will be looking at your design after you're done, since it doesn't tell them what the overridden text is for or why it's styled that way.
Are the overrides coming in a specific region? If so, them a style definition like div.left_nav p {/*styles*/} might be a better fit.
Lastly, Is your default <p> styling not really default? Maybe a more loosely specified p style might be in order, with additional p.foo and p.bar definitions later on.
This doesn't fix your immediate problem, but it might be worth chewing on before you start your next project.
You can use inline styling to override the default styling.
<p style="background-color: #ffffff">white bg</p>
Inline styles have the highest precedence. The only styles that have higher precedence than inline styles are user styles applied by the readers themselves.
Just to check. For all the talk of "default styles", if you set the style for a type of element in a CSS file, e.g.:-
li {...}
Then you also include a css file that contains a class definition and apply that class to an individual instance of that element type, e.g.:-
<li class="myLiClass">Some Text</li>
From what I understand it is impossible to get the class myLiClass to override any attribute of the style specification "li {...}" for the element by providing that overriding style in a css class.
Therefore I assert that this means:-
"If you specify a style attribute for any html element type (element type, not a class) in a css file, then all pages that use that css file cannot show that element type attribute using any different styling, where that different styling is stated as a css class."
Can anyone confirm this with an absolute yes, or a working example of why this assertion is not true.
You can apply the style for your tag from your stylesheet like this:
CSS
p.first{ color: blue; }
p.second{ color: red; }
HTML
<html>
<body>
<p>This is a normal paragraph.</p>
<p class="first">This is a paragraph that uses the p.first CSS code!</p>
<p class="second">This is a paragraph that uses the p.second CSS code!</p>
</body>
</html>
I would agree that there isn't really a "Default" style for a tag since each browser has significant freedom on how to display it.
I think the easiest answer is to rethink the problem - define a class that you use for all P tags and then if you fail to use the class it will give you the default styling.
<style>
p.all {margin.top:9px;}
</style>
<p>This would be default style</p>
<p class="all">This would have your style</p>
Alternately, if you wrapped all of your stylized content in a div or some other tag, you could nest the styles like this:
<style>
div.foo p{border:1px solid black;}
</style>
<p>normal</p>
<div class="foo">
<p>abnormal</p>
</div>
Hope this helps.
What makes this impossible is that there is no "default style".
Default styles come from the browser's internal style sheet and the user's preferences. So different browsers and different users have different defaults.
You could assume that white/transparent background, black foreground and Arial font were going to be most people's default styles, but you couldn't be sure.
So, like other people are saying, you have a fundamental problem because you've got a style for all P elements, and there's no way to code a P which doesn't inherit from that style, you can only over-ride it using CSS of greater specificity.