Err...At the top of the page? It looks like a HTTP header, based on the last line. Also, in URL encoding, the 2 digits following a \'%\' character is a hex byte, and I see alot of \'%\'s in that string...
Bah, any help? No? Well, I think its something wrong with a) the server, b) the forum script, or c) your browser. Does it do it on anyone elses computer? Not mine.