Help! [Firefox]

Ok, this is a slightly difficult problem to explain but hopefully any techno heads around might be able to help me.

Usually, when I am on a webpage and I push the down arrow on my keyboard, it brings me down the page gradually. However, since this morning when I do that in Firefox it acts like it is a word processor, with a cursor attaching to words and when I press down it brings me down line by line.

It isn't happening in Internet Explorer and I can't find any options in Firefox to stop it.

Any ideas?

Edit:

Fixed it - hooray for google!

Anyone who has the same problem, just whack F7!

I don't know if this will help but I found a setting which might be your one under edit>>preferences>>advanced>>general>>accessibility >>always use cursor keys to navigate within pages. Switch it off if you find that

F7 - cool. Caret Browsing it's called. That's something we both learned today.