The great resource BrowserShots tells me that there's a rendering problem with these pages in IE 6 (that last one is a link to the screenshots, but I'm not sure how long they'll stay).
Sigh.
It looks like a box-model issue with the center column running too wide. I'll see if I can tweak it into position tomorrow -- hopefully without doing rendering conditionals for IE 6.
It's odd, though, that it seems to work fine in IE 5.5, so it was some odd bug added just in 6.0.
All of the others Windows browsers that they show work fine except for the "Partners" box that slips to the top of the page on any of them that don't know what min-height means. (But I knew that would happen and it's not all that bad.)
BrowserShots isn't showing what things look like on Mac, but I've just downloaded the Windows version of Safari, so I can now be more confident that what works in IE7 and FireFox 2 is also working in Safari.
But whatever it looks like elsewhere, IE 6 is still the third most popular browser on the site after FireFox 2 and IE 7, so I must deal with this oddity.
[Update -- 11/11:] Looking at the screen shots more closely, I see that IE 5.5's expected box-model problems cause the three images in the feature boxes (under "now in Q" header to wrap. Not many users of that browser any more, but I'll try to fix it with a hidden overflow.
IE 6 issue is fixed by cutting two px off each side of the padding. That puts things a bit too close on the left, however, so I'll see if it works by cutting only two total.
The padding for the center (main content) column was 10px on both sides. I've now changed it to 10px on the left and 7px on the right, which fixes the IE 6 issue on the home page. (I haven't yet tried interior pages, but they all inherit the padding values even when they change the width of that column. I'll have to make sure they're working, however.
The IE 5.5 wrapping issue isn't worth worrying about at this point. Trying to fix it with overflow:hidden and an explicit width on the containing element causes a cascade of issues in IE 7. So, basically, I'll leave it alone. I suspect that those who still use IE 5.5 are accustomed to weird-looking pages.