What is a 500 server internal error [Solved]

[krillmeed]

I seem to be getting quiet a few of these 500 errors on my forum and they come and go. Can someone tell me roughly was causes them? Are they a problem with the forum or with the server itself? I have reported this to yahoo my server, and they come and go, with no explanation if they have done something, or i have made a mistake. Any advice or experiences would be appreciated, before Yahoo gets there shovel out and starts giving out a lot of manure about the problem <img>

[Helter]

http://www.checkupdown.com/status/E500.html

[krillmeed]

Thanks that explains everything <img>