I think it's rather a content filter on a firewall or whatever. If you can find out what kind of content filter your company is using you may can get the website categorised by the vendor of the content filter.
if it's websense: you can look it up here: https://www.websense.com/content/Sitelookup.aspx it requires a login though. it seems that you can register for free. i haven't done it, so i don't know for sure.