Font Horror

Lynn, we have just upgraded our operating system to Debian 4 and are now using Iceweasel 2.0.0.3 instead of whatever old version of Firefox was kicking around. In doing this something strange has happened to the TNH fonts - I'm getting a rather illegible serif font in for the main content of the site and the right hand column. I used my edit, preferences, content function, which altered the text under the adverts, but nothing else. Is there any way to change to a sans serif?

Thanks

Zillah