External CSS
When you need to make changes to several pages, you often use the external style sheet.
It is perfect in this situation because it enables you to alter just one file to alter the appearance of the complete website.
It uses the <link> tag on every page and the <link> tag should be put inside the head section.
Example:
<head><link rel="stylesheet" type="text/css" href="mystyle.css"></head>
Advantages of External CSS:
The style of several documents can be controlled from the site by using them.
Multiple HTML elements can have many documents, where classes can be created.
To group styles in complex situations, selector and grouping methods are used.
Disadvantages of External CSS:
An extra download is needed to import documents having style information.
To render the document, the external style sheet should be loaded.
Not practical for small style definitions.