How can I report a malicious website?

I did a search on how many megabites equals a gigabite. On MSN live search. On the first one it reads: “How many MB is equal to 1 Gigabyte Equals GB in computer bytes …”
When I went there it was a blank page, but it had like a you tube thing. I did do a DUMB thing it said I needed to do an update in order to view – YEP!! I did. I am so infected you can’t believe it. Our IT guy cleaned it up… I went back to see what the page again… I could NOT get out of the page or anything and the virus is back…. this is a PORN thing… I would like to report it as I don’t want anyone to have this experince!!! Please let me know what to do!!