$lang['Username_taken'] = 'Sorry, but this username has already been taken. If this is your username then you need to log in.';
This makes it so that when a guest tries to write a message using a name that is already registered, you get this...
But how can I make it so the word, log in is a link to the log in page? Underlined of course. Prefferably I would want it so this link works even if I change the directory of my forum.
Any help is appreciated.