If you want to use your style sheet to various pages, then it’s always recommended to define a common style sheet in a separate file. A cascading style sheet file has extension .css and it will be included in HTML files using <link> tag.
The HTML <link> tag is used to specify relationships between the current document and external resource.
Following is an example to link an external style sheet file available in css sub-directory within web root:
<link rel="stylesheet" type="text/css" href="/css/style.css">
Example: Now let's make above Example using External CSS: