Applying CSS Styles Only to Certain Elements

Apply CSS styles to an element depending on its child elements - ONLY CSS

You can't select a parent element from inside any of its descendants.

However you can make an item looks like selected. The trick is to add position: relative on outermost parent and use :before or :after pseudo element on the child element.

Here is the css code:

.chatrow_1 {
  position: relative;
}

[data-user="1"]:before {
  background: skyblue;
  position: absolute;
  z-index: -1;
  content: '';
  bottom: 0;
  right: 0;
  left: 0;
  top: 0;
}

.chatrow_1 {  position: relative;}
[data-user="1"]:before {  background: skyblue;  position: absolute;  z-index: -1;  content: '';  bottom: 0;  right: 0;  left: 0;  top: 0;}

<div id="chat">  <p class="chatrow_1">    <span class="time">      01:41:55    </span>    <span class="user-msg">      <span class="c-avatar">        <img src="" alt="Image Description" />      </span>      <span class="user">        <strong>          <span class="chat-username" data-user="1">            Anonymous_001          </span>        </strong>      </span>      <span class="msg">        <span class="chat-msg">Hello</span>      </span>    </span>  </p>  <p class="chatrow_1">    <span class="time">      01:41:55    </span>    <span class="user-msg">      <span class="c-avatar">        <img src="" alt="Image Description" />      </span>      <span class="user">        <strong>          <span class="chat-username" data-user="2">            Anonymous_001          </span>        </strong>      </span>      <span class="msg">        <span class="chat-msg">Hello</span>      </span>    </span>  </p></div>

Applying CSS styles only to certain elements

The final fix was to use SASS (recommended by someone off-site), as that allows you to nest elements and then automatically produce the final CSS. Step by step the process is:

Concatenate the two Bootstrap files (bootstrap.css and bootstrap-responsive.css) into bootstrap-all.css.
Create a new SASS file, bootstrap-all.scss, with the content div.bootstrap {.
Append bootstrap-all.css to bootstrap-all.scss.
Close the div.bootstrap selector by appending } to bootstrap-all.scss.
Run SASS on bootstrap-all.scss to produce a final CSS file.
Run YUI Compressor on the final file to produce a minimised version.
Add minimised version to head element and wrap everything I want the styles to apply to in <div class="bootstrap"></div>.

How to add a style only to certain elements of a list via CSS

You can write something like,

.the_list li:nth-child(1),
.the_list li:nth-child(2) {
    border-bottom: 1px solid tomato;
}

So the above selector will select the first and the second child of your ul element with the class of the_list

Demo

If you want to support vintage browsers like IE8, you can also do something like

.the_list li:first-child,
.the_list li:first-child + li {
    border-bottom: 1px solid tomato;
}

Demo 2

So here in the second selector, we are first selecting the first li element nested under ul with a class of the_list and then we select adjacent li to the first child.

How can i apply css stylesheet to single specific element?

There's lots of ways to accomplish this. There's lots of css selectors like ID, classes... See css selectors reference

Best way to achieve what you want is to use classss. See classes

.red {      color: red;}.blue {      color: blue;}

<label class="blue">    I'm blue</label><label class="red">  I'm red</label>

Apply CSS Style on all elements except with a SPECIFIC ID

Use the :not selector:

div:not(#bar){    color:red;}

<div>foo</div><div id="bar">bar</div>

Applying a stylesheet to only a certain region of an HTML file

It is not possible to do it directly using those CSS files that are distributed, but you can create namespaces for each CSS framework library (or CSS file) and use that wherever you want to use that framework features.

See How to namespace Twitter Bootstrap so styles don't conflict and Is there any ready to use Bootstrap css file with prefix for more details on how to namespace your style-sheets.

If you're using less, then you can create a namespace by adding a pregfix to bootstrap like this:

.bootstrap-styles {
  @import 'bootstrap';
}

/* OR */

.bootstrap-styles {
  @import (less) url("bootstrap.css");
}

You can use http://www.css-prefix.com/ to prefix any CSS file and then use it like this:

<header class="bootstrap-ns-prefix> (some bootstrap code inside) </header>

<main class="style2-ns-prefix"> (some other framework/css styles that don't get affected by bootstrap) </main>

EDIT

It does not work automatically, you have to namespace each of your CSS and then use those CSS files instead of the initials. The generator www.css-prefix.com works for me, but it adds some extra classes/namespaces at the beginning/end and before/after each comment; you should check that and correct/delete any errors before you proceed. As I mentioned above, you can use LESS or SASS frameworks to generate those namespaces.

Here is an example of using both Bootstrap and jQuery UI together:

<head>
...
<link rel="stylesheet" href="css/bootstrap_ns.css">
<link rel="stylesheet" href="css/jqueryui_ns.css">
...
</head>
<body>

<button class="btn btn-primary">Test Button</button>

<div class="bootstrap-ns">
 <button class="btn btn-primary">Bootstrap Button</button>
</div>

<div class="jqui-ns">
 <button id="jqbtn" class="btn btn-primary">jQuery UI Button</button>
</div>

<script type="text/javascript">
jQuery(function($) {
    $('#jqbtn').button();
});
</script>
</body>

And the result is this one:

CSS namespaces

As you can see, all three buttons have the bootstrap button classes btn btn-primary but only the button inside bootstrap-ns container uses the bootstrap styles.

Here you can see a demo page: http://zikro.gr/dbg/html/bootstrap-ns/

Here you can check bootstrap.css and jquery.ui.css generated by www.css-prefix.com and manual cleaned.

Applying CSS styles to all elements inside a DIV

You could try:

#applyCSS .ui-bar-a {property:value}
#applyCSS .ui-bar-a .ui-link-inherit {property:value}

Etc, etc... Is that what you're looking for?