Comment it out.
Find the line referencing the style sheet.
HTML Code:
<link href="/your.css" rel="stylesheet" type="text/css" />
and add
HTML Code:
<!-- up front and --> to back.
whole thing looks like this.
HTML Code:
<!--<link href="/your.css" rel="stylesheet" type="text/css" />-->
You can also use it to leave non rendering notes in your code like,
HTML Code:
<!--BEGIN HEADER-->
<!--END HEADER-->
You can use it to disable entire sections of code.