It depends on what you are linking to. Links to other sites that have forums are not allowed. Hotlinking of photos is not allowed. If you want to like to another site with information, you can copy and past the link into the window that opens when you click on the globe with a link of chain in front of it above where you type in the post. Images you can just use the IMG code, again as long as they are not hotlinked from another site.