Version 0.1

This script removes the about.com-imposed vertical size restriction of 500 pixels for signatures.

But if large signatures bug you, you can easily use the script to impose an even more restrictive policy: just change the value 'max-height:none' to 'max-height:250px' to restrict the displayed signature size to 250 pixels. You can use any value you like, and a value of 0 pixels would display no signature - though there is an in-built forum function for that and another script of mine, too.