In firefox only, i cant use the enter button at all on any web forms and forums.

I can though use it as normal in every other program, and other browsers. (wrote this in notepad to seperate paragraphs in case anyone was wondering).

Is there any setting that can change this that i may of accidentally clicked on with a mash of buttons on the keyboard? It was working fine earlier today and i cant remember what i could of pressed that could of done this..ive gone through all the firefox options and cant see anything in there would change the enter button behaviour....