As always, it depends on the context. I promote homopunk.com, for example, but it works in that context...

If you mean sites whose texts are like "two homos fuck" and whatnot, well it certainly sounds inappropriate, although i think it's as much a communication breakdown as anything. Homosexual is probably the most internationally recognized word for "gay" after the word "gay" itself, so you can't blame non-English speaking sites for using the word -- they could just as easily be thinking it's a shortened form of "homosexual" and don't realize the negative connotations it carries for native English speakers.