Css Font Size

I am working on a website and want to have buttons the user can click to change the font size. The website is entirely CSS and want it to link to something in a stylesheet (inline, or whatever). Does anyone know how to do this?

I was looking at www.cbs4denver.com, but it is far too confusing to find out what is going on and was wondering if anyone knows how.

the ol' CSS zen garden uses the following format:

Code:

<a href="?cssfile=/filename.css&amp;page=0">text</a>

so I'm assuming if you do it that way, you'd just put something like the following in your head element:

Code:

<link type="text/css" rel="stylesheet" href="<? echo $cssfile; ?>" />

(I ignored the

Code:

page=0

part since I have no idea what it does.)