why do signatures only have to be a specific size?
Signatures must be no bigger than 500 x 200 pixels (width x height). They can be smaller than this but must not be any bigger.
The reason for this is because the bigger signatures are the more space they use on the server.
I have noticed on many other forums that people upload HUGE signatures and I've always found this makes a forum look messy. Also, some members might not have a fast internet connection which means images on the forum can take longer to appear than they do for members who use broadband for example.