The problem is people that use IE demand accessibility features. These users should use something like Firefox that makes simple things like font size adjustment available on every page, regardless of whether the site designer has planned for them. Using em's in CSS is ridiculous. A while back all the standards guys thought it was cool and everyone adopted it. Even their sites are back to their static selves these days. Unfortunately, as you have seen, hardcoding relative font sizes causes a whole other set of problems.

If you need accessibility, download a browser that actually cares about you, and stop sending site designers running around writing 300 lines of code to replace one because your browser uses rendering concepts from 1991.

vBulletin doesn't help. Take a look at the code on even their default template. Endless lines of CSS including browser hacks galore. Apparently if you can trick the w3c into validating your page you're justified in advertising a standards compliant forum.

Such a nightmare! Good luck!