I know that some editors in some categories don't allow it, because websites can change constantly, and in 2 years it might not even be online at all. Perhaps rather than giving a direct link, you could mention that there is more to learn on the subject and say something like "There are many websites out there about Mr. Jones and his tomato plants. Look them up if you're interested" or something like that.
Edited to add: there are some exceptions, for example if you're doing a direct quote. In that case, though, I think it's still better to say something like "On his band's official website Mr. X says ....." rather than giving the exact link.
Edited by guitargoddess (Wed Feb 25 2009 05:52 PM)
Editor: Television and Animals