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Three Ways to Insert CSS
When a browser reads a style sheet, it will format the document according to it. There are three ways of inserting a style sheet:
  • external style sheet,
  • internal style sheet, and
  • inline styles.

External Style Sheet
An external style sheet is ideal 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.

Each page must link to the style sheet using the <link> tag. The <link> tag goes inside the head section: 
 <head>
  <link rel="stylesheet"
    type="text/css"
    href="5.css" />
 </head>

The browser will read the style definitions from the file 5.css, and format the document according to it. An external style sheet can be written in any text editor.

The file should not contain any HTML tags. Your style sheet should be saved with a .css extension. An example of a style sheet file is shown on the right:
5.css 
 h3 { color: #3366CC }
 p  { margin-left: 20px }
 body { background-image:
  url( "bg.jpg" ) }

†Do NOT leave spaces between the property value and the units! If you use “margin-left: 20 px” instead of “margin-left: 20px” it will only work properly in IE6 but it will not work in Mozilla/Firefox or Netscape.


Demonstration
The following demonstration shows how the script of HTML and CSS is displayed on the Web: