How is it possible to override styles specified in another style sheet?
I do not want to use the !important tag to override them. I would much rather specify a new style sheet, put styles in there. Could this be achieved by changing the load order of the style sheets?
It depends. CSS stands for Cascading Style Sheets, and there's a specific order that styles are applied in, overwriting previous styles. Without going into too much detail:
If your rules have the same specificity, just load your stylesheet second and everything will work fine.
If your rules have higher specificity, the order won't matter.
If your rules have lower specificity, you'll need to modify them to match.
So, what's specificity? Basically, it's the sum of each selector in a rule. So this:
a {
background-color: black;
color: white;
}
Has less specificity than this:
body a {
color: orange;
}
ID selectors have higher specificity than class selectors, which have the same specificity as pseudo-class selectors, which have higher specificity than tag selectors. So if all your content is contained in a <div> with an id of content, you would be able to override a style that looks like this:
body a {
border: 0;
}
With:
#content a {
border: 1px solid black;
}
The boostrap stylesheet should be loaded first, your stylesheet second, this way your overwrites will be picked up.
This is called "cascading", from the documentation:
Cascading
This is the capability provided by some style sheet languages such as CSS to allow style information from several sources to be blended
together. These could be, for instance, corporate style guidelines,
styles common to a group of documents, and styles specific to a single
document. By storing these separately, style sheets can be reused,
simplifying authoring and making more effective use of network
caching. The cascade defines an ordered sequence of style sheets where
rules in later sheets have greater precedence than earlier ones. Not
all style sheet languages support cascading.
If you can increase the specificity of styles, you can do this without the !important.
For example:
HTML
<div id="selector">
<a>Hello</a>
<a class="specific">Hi</a>
</div>
CSS
div a {}
Will be ignored, if you give a specific class inside #selector
.specific { }
Here is a demo explaining my point. Basically, the idea is to define the styles as closely as possible.
look at http://www.stuffandnonsense.co.uk/archives/css_specificity_wars.html.
<p class="example">
This is a <strong>test</strong>.
</p>
strong { color: red; }
p strong { color: green; }
p.example strong { color: blue; }
The text will be blue. The order of the rules doesn't matter.
Related
Is it possible to make the entire .class CSS selector important? I'm thinking in this kind of structure:
.custom-selector !important {
display: inline-block;
vertical-align: middle;
position: relative;
padding-left: 5px;
}
I don't know if it's possible.
No, it's not possible. !important is thought to be an instrument of last resort and as such should be used sparingly. !importanting whole selectors would caricature that idea.
If you need to trump other styles, use CSS specificity to your advantage. You can use, e.g., these techniques to push your style declarations to the top:
double class name will trump single class name:
.custom-selector.custom-selector > .custom-selector
ID trumps class:
#custom-id > .custom-class
IDs can be duplicated, too:
#id#id > #id
inline styles trump any stylesheets:
<style>
p#id#id.class.class { color: green; }
</style>
<p id="id" class="class" style="color:red">I am red!</p>
First off !important applies to one specific declaration in a CSS rule. It doesn't apply to a class. So, "no" you can't make a class !important.
Second off, !important is just one part of CSS specificity. You can also use other ways to make a rule be a more specific rule to have precedence (such as referring to an id in the parent chain instead of just the class. When I'm writing CSS, using !important is my last possible choice - I'd much rather solve overrides with other specificity solutions. Usually, if you control all the CSS, this is pretty easy to avoid using !important. If you have to override some CSS that you don't control, then sometimes it is handy.
Check this question here for more details. As it explains things better.
I just found the :root pseudo class.
The :root CSS pseudo-class matches the root element of a tree representing the document. Applied to HTML, :root represents the element and is identical to the selector html, except that its specificity is higher.
https://developer.mozilla.org/en-US/docs/Web/CSS/:root
What exactly is it used for? Why would anyone ever use it aside from higher specificity when you can just use the html selector?
The answer here is:
except that its specificity is higher.
And why does it matter?
In a normal CSS scenario, if you have something like this:
html {
background-color: red;
}
html {
background-color: blue;
}
You will get the blue background, because it's evaluated last. You can see here.
But, if you have this instead:
:root {
background-color: red;
}
html {
background-color: blue;
}
You'll get the red background. You can see here.
Imagine a scenario where you import several libraries and some of then set some properties on the html that you want to get rid of. You can define your properties as !important, you can organize your imports so what you want is evaluated last or you can use the :root selector.
Others Scenarios
As pointed by #user2864740 and #13ruce1337, CSS is not only applied to HTML, but it can be applied to any kind of XML document, including plain XML, SVG and XUL. The :root pseudo class will select the root of other types of document correctly.
In my CSS, I have this:
b {
color: Red;
}
And in my body:
<b>Hello world!</b>
As a result, I get "Hello world!" text that is red in color.
However, as I add more classes:
.myClass {
color: Blue;
}
.green {
color: Green;
}
And I modify my body:
<b>H<a class="myClass">ell</a><a class="green">o</a> wo<a style="color: Black;">rl</a>d
I will not get the same result as earlier.
Is there a way to strictly set a CSS style? Which means that with the above code I wish to get "Hello world!" text that is red.
Thanks
This is a question of CSS Specificicty
The concept: Specificity is the means by which a browser decides which
property values are the most relevant to an element and gets to be
applied. Specificity is only based on the matching rules which are
composed of selectors of different sorts.
Inline styles override external CSS, and class selectors override element level selectors.
The following list of selectors is by increasing specificity:
Universal selectors
Type selectors <--- your b CSS
Class selectors <---- your .xyz CSS
Attributes selectors
Pseudo-classes
ID selectors
Inline style <--- your style=''
If you wish to override specificity, you can use !important after the rule in question, e.g.:
b {
color: Red !important;
}
However, this is not recommended, instead you should write 'better' rules (more specific) to target your HTML as appropriate. This ensures you end up with better structured code, the issue with !important being it can lead to unforeseen circumstances where rules aren't working because you may have forgot you had previously overridden them.
Again, from MDN:
The !important exception
When an !important rule is used on a style declaration, this
declaration overrides any other declaration made in the CSS, wherever
it is in the declaration list. Although, !important has nothing to do
with specificity. Using !important is bad practice because it makes
debugging hard since you break the natural cascading in your
stylesheets.
Some rules of thumb
Never use !important on site-wide css. Only use !important on
page-specific css that overrides site-wide or foreign css (from ExtJs
or YUI for example). Never use !important when you're writing a
plugin/mashup. Always look for a way to use specificity before even
considering !important
With the markup that you provided, no. Otherwise, maybe
The inline style has priority over the stylesheet so part of the text will be black no matter what. You might be able to create a rule that has enough specificity that it will take precendence over any other rules.
b, b .myClass, b .green {
color: red;
}
Though this can get troublesome to maintain. And there is still a chance that a different css rule will get higher precedence later on. I am not completely sure that even specifying all the children with * will do it.
You seem to be asking whether you can set a property (color in the example) on an element in a manner that will not be overridden by settings on inner elements.
You cannot do that with settings on the element itself. But you can set a property on an element and all of its descendants:
b, b * {
color: Red !important;
}
This will override any normal settings for color on inner elements. But it is ineffective against, say, .green { color: Green !important; }. To defeat that, you would need a more specific selector, such as b .green, for your rule—so there is no general way to achieve that (i.e., a way that is independent of the specific markup used inside the element).
in my html I have
<div id="mainNewsBody" class="news">
<a class="readMore" href="/News/Details/1">read more ...</a>
</div>
I tried to style read more ... snipper with this css
#mainNewsBody .news .readMore a{
color: #7F0609;
}
to actually apply this style I have to use !important keyword in color property.
I know that this !important keyword force to use that property but I do not understand why that is the case here, because I explicitly told to match on particular id with particular class element and inside that element to mach link.
Can someone englight me.
Thanks
Try this one:
.news .readMore {
color: #7F0609;
}
There's no need to call for id and class name for the same element.
It's a.readMore instead of .readMore a (the first case would search for an element with class .readMore and append the CSS to any children a-elements)
and #mainNewsBody .news should be #mainNewsBody.news (you should 'concatenate' the id and class since they refer to the same element)
making a total of #mainNewsBody.news a.readMore
Fiddle
EDIT
I see many notes on simplifying your css to just classes. This really depends on what you're trying to accomplish. If you're working with a huge CSS file, I'd recommend specifying as strict as possible. This to prevent any CSS being applied on places where you don't want it to.
a { } for example will mess with all your links, a.news { } will only mess with a class='news'
It'd the specificity which is troubling you, the more elements class id you have in your selector, more specific your selector is.
So for example
.class a {
}
is more specific than just
a {
}
Just see to it that you do not have a more specific selector, if you've than you need to make the current one more specific or use !important declaration as you stated.
In the above snippet this is incorrect
#mainNewsBody .news .readMore a
It will search for an element having class news inside an element having an id mainNewsBody which is not true in your case so either use this
#mainNewsBody a.readMore {
/* This will be more specific than the below one
as you are using id here and not class */
color: #7F0609;
}
Or use
.news a.readMore {
color: #7F0609;
}
Ozan is right, remove the "mainNewsBody" ID from the CSS if it's not absolutely necessary.
.news .readMore a{
color: #7F0609;}
If you want to be really specific and need to include the ID in the CSS selector remove the space from in-front of ".news"
#mainNewsBody.news .readMore a{
color: #7F0609;}
CSS Tricks - Multiple Class ID Selectors
CSS rules marked !important take precedence over later rules. !important ensures that this rule has precedence.
Probably your code is generating inline css for the a element, or you have another less specific definition for a element with !important keyword somewhere else.
Inline styles have priority higher than styles defined outside the element. To overcome the inline style or a style with !important keyword by a less specific definition, you need to define it by the keyword !important and a more specific definition.
In designing the HTML and CSS for a page, when should I use
img.className
versus
.className
versus
#idName
or some other variant?
Are there guidelines or recommendations?
Summary from answers
Thank you to all answerers - there is some excellent stuff here!
make CSS as specific as possible
use an OO approach
order: #id, tag, tag.className, .className
when to use each selector, also class/ID comparison
give selectors names based on purpose, not what they look like
use advanced selectors for smaller code, leave CSS classes for exceptions/overrides only
manage ASP.NET munging ID
In general you should be as specific as the item demands.
There is no general rule, it depends on the style in question.
A lot of people will recommend you keep to the lowest specificity with the theory that this allows the maximum cascading reuse but this is absolutely toxic in real world situations where you have multiple developers all working on slightly different versions of what a .foo might look like. Pollution from inheritance you did not want leads to massive bloat in trying to undo that locally or time-loss in refactoring.
The best guideline I always offer is to try and think of CSS in OO terms: class selectors map to interfaces more or less, tags map to classes, and ID selectors map to instances. Consequently decide if the style you want to apply really applies to that thing, all things like it, or anything which wants it.
I also strongly encourage you to make use of high level IDs on wrapper elements so you can write selectors in a namespace like fashion (i.e. #foo .bar, #foo .baz where #foo is unique to a page or set of page designs) which allows you both a level of specificity which reduces cross-design pollution and a level of generality which lets you make the most of cascading CSS reuse.
Best of both worlds.
It depends on the intended semantics, and, as others said, be as specific as possible.
#idName for unique elements on the page. Good examples are #header and #footer
TAGNAME for general purpose page styling.
TAG.classname and .classname for exceptions/overrides to the above rules.
And don't forget the use of advanced selectors. A bad example:
<style>
H1{ font-size: 200%; color: #008; }
#mainMenu { color: #800; }
.in_the_menu { color: #800; font-size: 150%; }
</style>
<h1>Hello World!</h1>
<div id="mainMenu">
<h1 class="in_the_menu">My Menu</h1>
</div>
The same could have been achieved with:
<style>
H1{ font-size: 200%; color: #008; }
#mainMenu { color: #800; }
#mainMenu H1 { color: #800; font-size: 150%; }
</style>
<h1>Hello World!</h1>
<div id="mainMenu">
<h1>My Menu</h1>
</div>
The second example gets rid of the superflous "class" attribute on the H1 element in the "mainMenu" div. This has two important benefits:
The HTML code is smaller and cleaner
You are less likely to forget to add the class attribute
If you take good care of you CSS, and make use of proper advanced selectors, you can nearly completely leave out CSS classes. And keep them only for exceptions/overrides.
Take this example which draws boxes with headers:
#content H2{
border: 1px solid #008789;
padding: 0em 1em;
margin: 0.2em 0em;
margin-bottom: 1em;
font-size: 100%;
background: #cccb79
}
#content H2 + DIV{
margin-top: -1em;
border-left: 1px solid #008789;
border-right: 1px solid #008789;
border-bottom: 1px solid #008789;
margin-bottom: 1em;
}
Now, as soon as you follow a H2 with a DIV in the #content element, you have a nice box. other DIVs and H2s are left alone:
<div id="content">
<h2>Hello Box!</h2>
<div>Some text</div>
<div>Some more text</div>
<div>Some more text</div>
<h2>And another title</h2>
</div>
If you get these rules right, you hardly ever need classes, and can work with IDs and TAG names alone. And as an added bonus, your HTML will be a lot nicer to read and maintain.
You preference should be, in order from highest to lowest:
id
tag
tag.className
.className
ID selectors are fast. Tag selectors are reasonably fast. Pure class selectors are slow because the browser essentially has to interrogate every element and see if each has that class. Getting elements by ID or tag name are "native" operations from a browser's context.
Also, I find it good practice to make your CSS selectors as restrictive as possible otherwise it just turns into a mess and you end up getting all sorts of unintended consequences where CSS rules apply where you didn't otherwise expect, which often forces you to create a similar yet different selector just so none of the rules regarding the first don't apply (translating into more mess).
Basically if you know if you only use a class on div elements then do this
div.className
not
.className
If you apply a class to several elements just list them:
h1.selected, h2.selected, h3.selected
instead of
.selected
In practice I find very few situations where you need to use "naked" class selectors or where it is advisable to do so.
you should use the selector best describing your rules
id: when you want to select one single element
.classname: when you want to style elements regardless of their tag
tag.classname: when you want to style only tags with the given class
tag tag tag: when you want to style all subelements of a tag
Class selectors
.className
This is to be used when you have more than one element on the page that you would like to apply the same style to. It can be to any tag element. So in the following all will use the same style as set out by the .className.
<p class="className"></p>
<img src="/path/to/image.png" class="className" />
But you can also restrict it like so:
img.className
By placing the tag along with the style definition, you're saying that this style is only to be used when it's the class used by that particular tag, in this case, an image.
HTML code will look like this:
<img src="/path/to/image.png" class="className" />
If you have other elements on the page using the same class style, but are not of the same tag, then the styles set out in this will not be applied and they will take on the more generic version as mentioned in the first example.
So repeating the example above:
<p class="className"></p>
<img src="/path/to/image.png" class="className" />
Only the image will take on the style as set out by img.className whereas all the rest will take on the style rules set in .className.
ID selectors
#idName
This is to be used when there is only one instance of a particular element that you wish to apply the style to.
You can also force it to apply only in certain tag conditions as you have earlier with the class definitions.
p#idName
This example will only apply to the paragraph block marked with the ID:
<p id="idName">
If you were to put that id on another element, like this:
<div id="idName"></div>
Then it will not take on the style set out and be ignored.
As to your two first selectors, the first of the two will overwrite the second, as it's more specific. You can calculate the specificity of a selector.
One thing worth noting is that some server side scripting technologies (most notably ASP.NET) don't play well with using IDs for your styling. If there is a chance your design will be used with such a technology, I recommend forgetting about #id selectors and use tag.className instead.
The reason is that ASP.NET actually changes the ID that ends up in the HTML based on a number of criteria, if the tag is output by a server side control.
I know this is a pretty old question but for all those who are reading this just now...
There are 4 categories of rules in general:
ID Rules, Class Rules, Tag Rules, Universal Rules.
And it's important to mention that class selectors are faster than tag selectors. So you should always use them in the following order
1. ID Selector
2. Class Selector
3. Tag Selector
4. Universal Selectors
In your case you should never use the tag name before class name.
You can find more information here: Writing efficient CSS
It really depends on the situation:
.error{
color:red;
}
p.error{
background-color:yellow;
}
div.error{
background-color:grey;
}
Always use the cascading effect of CSS to your advantage.
It's good practise to use the least specific rules you can for each rule.
How you structure your CSS will depend on the particular needs of the design.
Yes. You may want to use the same classname for two elements in the future. Be explicit and clear. This will also prevent class-rules from overlapping onto unintended elements.
h1.title { font-size:18px; } /* My h1's are big */
p.title { font-size:16px; } /* My p's are smaller */
.title { color:#336699; } /* All titles are blue */
Use ID's only when necessary, and only once per page.
When to use what depends on what you want to select. img.className (type selector + class selector) selects only IMG elements that’s in the class “className” while .className (just class selector) selects any element that’s in that class and #idName (id selector) any element with the ID “idName”.
But besides that, the selector all have a differente specificity that affects the order in which the properties of that rules overwrite the one of others.
So if you have an IMG element with the ID “idName” that’s in the class “className”:
<img src="…" id="idName" class="className">
The properties of the rules would be applied in the following order (specificity from highest to lowest):
#idName
img.className
.className
But when you use a specific class only for one specific type of elements (e.g. “className” only for IMG element), you can go with only .className.