You can use CssStyles with ASP.net page in different ways :-
n [HTML type]:-
External Style Sheet [Cascading 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="mystyle.css">
</head>
<link rel="stylesheet" type="text/css" href="mystyle.css">
</head>
