Huge web development tip: do your testing from IE6 from the get-go.
The site was finally finished, the layout approved by my coterie of nerd-testers, but as one last check I booted up IE6 on an old computer (IE7 was a mandatory install so I didn't have convenient access to it for testing on my development machine) and the layout was completely trashed in that browser. I could never be a fulltime web designer, issues like this would drive me nuts.
+1 week delay. Sigh...
