In order to include or link a stylesheet to the HTML page, use the link tag. The link tag is placed within the <head> and </head> part of the HTML page. Like so
<html> <head> <link rel="stylesheet" type="text/css" href="style.css"> </head> <body> </body> </html>
Notice the href attribute of the link tag; href points to the CSS file.
If the CSS file is in the same folder as the HTML, you can refer it by the file name. If, suppose the CSS file is in a sub folder style, refer to the CSS file like this:
<link rel="stylesheet" type="text/css" href="style/style.css">
Refer to the relative URL section in the HTML tutorial for more information on linking relative to the HTML page