I think the signature restrictions need to be rewritten.
A web page will look different on each computer. There is too many variables for the way a page looks. And they're different on each computer. Screen resolution, what's on the left and right side of the browser, the size of the browser, the browser itself, the font, etc.
So a person can't be really sure if their signature is too big. If you minimize the browser, then decrease the length, the page will grow longer. If you increase the length, the page will grow shorter. In fact, those with 21-inch monitors may not even think their signature is very long.