Detecting when styles disabled

Question

What's the best way to detect, with JS, if the user has disabled your stylesheets? Is there a reliable way even?

Answer 1

How about asking them?

<div style="display:none">This site relies on CSS, please go to our <a href="noncss.html">CSS free version of this site</a></div>

Answer 2

Something easy would be to check the body background color for instance.

However, how likely is it someone disables CSS and not Javascript? (dunno what you use it for obviously)