HTML is usually not a good thing to allow in forum posts because you can do way to much with it (read: bad things)
So they created their own style of code to basically substitute as the HTML called BBcode (BB for bulletin board)
You can find out how they are coded by clicking on one of the icons in the editor template.
The most comonly used ones are [ url ] bleh.com [/ url ] that will make a link clickable and [ url= bleh.com ] yay [/ url ] will make the word "yay" clickable.
Others are [ b ] yay [/ b ] for bold, I for italic, U for underline, and there are also many others.
Of course always remove the spaces.
thank-you
EDIT: I think its about time to let Arn know i would have no problem with helping out the forum with any forum specific needs. 😛