Forum:User name in link

I know I've seen this done before somewhere, but cannot seem to replicate it. When you enter a link into the url with something like "username" in it, it would input your user name there. I'm not sure if this only works when manually placing it into the address bar, but would really like to know what this word is. Note I do not need to have the name actually show. 16:36, August 20, 2012 (UTC)