I almost always see URLS one way, like this:

http://www.domain.tld/script.php?key=value&key2=value2

on SMF forums, their urls look like this:

http://www.domain.tld/script.php?key=value;key2=value2.

when i tried to do that kind of url on my site, it spat an error at me. I was just wondering how they got that to work, and why they would want to do it differently?