CSS - Inclusion

There are four ways to associate styles with your HTML document. Most commonly used methods are inline CSS and External CSS.

Embedded CSS - The <style> Element:

You can put your CSS rules into an HTML document using the <style> element. This tag is placed inside <head>...</head> tags. Rules defined using this syntax will be applied to all the elements available in the document. Here is the generic syntax:

<head>
<style type="text/css" media="...">
Style Rules
............
</style>
</head>

Attributes:

Attributes associated with <style> elements are:

Attribute	Value	Description
type	text/css	Specifies the style sheet language as a content-type (MIME type). This is required attribute.
media	screen tty tv projection handheld print braille aural all	Specifies the device the document will be displayed on. Default value is all. This is optional attribute.

Example:

Following is the example of embed CSS based on above syntax:

<head>
<style type="text/css" media="all">
h1{
color: #36C;
}
</style>
</head>

Inline CSS - The style Attribute:

You can use style attribute of any HTML element to define style rules. These rules will be applied to that element only. Here is the generic syntax:

<element style="...style rules....">

Attributes:

Attribute	Value	Description
style	style rules	The value of style attribute is a combination of style declarations separated by semicolon (;).

Example:

Following is the example of inline CSS based on above syntax:

<h1 style ="color:#36C;"> This is inline CSS </h1>

This will produce following result:

This is inline CSS

External CSS - The <link> Element:

The <link> element can be used to include an external stylesheet file in your HTML document.

An external style sheet is a separate text file with .css extension. You define all the Style rules within this text file and then you can include this file in any HTML document using <link> element.

Here is the generic syntax of including external CSS file:

<head>
<link type="text/css" href="..." media="..." />
</head>

Attributes:

Attributes associated with <style> elements are:

Attribute	Value	Description
type	text/css	Specifies the style sheet language as a content-type (MIME type). This attribute is required.
href	URL	Specifies the style sheet file having Style rules. This attribute is a required.
media	screen tty tv projection handheld print braille aural all	Specifies the device the document will be displayed on. Default value is all. This is optional attribute.

Example:

Consider a simple style sheet file with a name mystyle.css having the following rules:

h1, h2, h3 {
color: #36C;
font-weight: normal;
letter-spacing: .4em;
margin-bottom: 1em;
text-transform: lowercase;
}

Now you can include this file mystyle.css in any HTML document as follows:

<head>
<link type="text/css" href="mystyle.css" media="all" />
</head>

Imported CSS - @import Rule:

@import is used to import an external stylesheet in a manner similar to the <link> element. Here is the generic syntax of @import rule.

<head>
<@import "URL";
</head>

Here URL is the URL of the style sheet file having style rules. You can use another syntax as well:

<head>
<@import url("URL");
</head>

Example:

Following is the example showing you how to import a style sheet file into HTML document:

<head>
@import "mystyle.css";
</head>

CSS Rules Overriding:

We have discussed four ways to include style sheet rules in a an HTML document. Here is the rule to override any Style Sheet Rule.

Any inline style sheet takes highest priority. So it will override any rule defined in <style>...</style> tags or rules defined in any external style sheet file.
Any rule defined in <style>...</style> tags will override rules defined in any external style sheet file.
Any rule defined in external style sheet file takes lowest priority and rules defined in this file will be applied only when above two rules are not applicable.

Handling old Browsers:

There are still many old browsers who do not support CSS. So we should take care while writing our Embedded CSS in an HTML document. The following snippet shows how you can use comment tags to hide CSS from older browsers:

<style type="text/css">
<!--
body, td {
   color: blue;
}
-->
</style>

CSS Comments:

Many times you may need to put additional comments in your style sheet blocks. So it is very easy to comment any part in style sheet. You simple put your comments inside /*.....this is a comment in style sheet.....*/.

You can use /* ....*/ to comment multi-line blocks in similar way you do in C and C++ programming languages.

Example:

/* This is an external style sheet file */
h1, h2, h3 {
color: #36C;
font-weight: normal;
letter-spacing: .4em;
margin-bottom: 1em;
text-transform: lowercase;
}
/* end of style rules. */