While cleaning up my current stylesheets (reducing size by removing some redundant elements), I decided to give alternate stylesheets a try. This technique is standard, but is not yet supported by all browers. This trick works for Netscape 6 and Mozilla, but not for Internet Explorer.
If you have such a browser, the alternate style should be available from a menu choice. (In Netscape 6, choose View | Use Stylesheet.)
For now, I created a new style called "Alternate" (dang, I'm creative) with a different background color and sans-serif fonts instead of serif.
Some references for further reading: