Two words: Internet Explorer.
I have been working on a website for a friend. It’s not quite ready for primetime, but It’s come a long way in 20 billable hours.
So, after a nap because my brain was tired, I decided to test it in Internet Explorer.
It didn’t render properly, either in regular mode of “compatibility mode” (It is to laugh). It worked in every other browser I had (Opera, for both Windows and Linux, Firefox, Konqueror, just to name a few) but not in IE.
It took me about 25 minutes and lots of creative language to find the tag that was causing IE to malform the page.