There's a bit of history around on startups.com and Stack Exchange.
Answers.onstartups.com was originally a Stack Exchange 1.0 community and was relaunched through area 51. After a rather long time, the proposal was closed for various reasons.
There are a few posts that have answers.onstartups.com links (as of this writing, 23 found via this search) that should be cleaned up... (I think I got most of them though there may be some residual cleanup to do... 90% of them were links to the same post by Joel again and again). Admittedly, that might take a bit of work to sleuth through http://www.brightjourney.com/ to find the corresponding post (assuming they grab the data dump - their Q&A clone doesn't use post IDs... they did grab the data dump, but not everything is there, they might have deleted some posts since then).
Onstartups.com still exists at http://onstartups.com and while they're pointing to a broken link for answers.onstartups.com themselves (SE doesn't own the onstartups.com domain).
As a note, the relaunch was relaunched again as http://startups.stackexchange.com and is still there if one is looking for content.