500 internal server error - showing up randomly

[as4s1n]

Occassionally, when I load up my website and click on any link, it will send me to a page that looks like this:

(Attach 1)

I was wondering if this was my fault or if not, to bring this to the attention of the admins in case it is an easy fix.

Also I get an occassional 503 'Service Temporarily Unavailable.'

It's getting pretty frequent actually. I removed the shtml pages so I knew which error it was.