It's webpages. For example, I often look at a webpage called
www.pandorasbox.com . Its a site devoted to a silent screen star called Louise Brooks. If I go to the message board forum all the avatars show up ok, apart from one, by a poster called Jolene an aquiantance of mine. Hers shows up as a blank box with a red cross in it.
Theres one or two other examples but thats the sort of thing I'm talking about.
By the way is it a good or a bad thing to use a proxy server?