I have a web site: http://txpub.usgs.gov/watershedreview/watershedreview.html that works fine in FireFox and Chrome but doesn't work in IE7 nor IE8. In IE7 the map is squished but the AJAX component works and in IE8 the map is fine but the AJAX doesn't work.
There are a few issues that browsers like Chrome and Firefox don't have problems with that IE does, for example, trailing commas. I've found tools like JSLint helpful in finding these issues, there's an online version of the tool here: http://www.jslint.com/
