I'm using Firefox 10.0

Sometimes after typing up a post when I hit the submit button I get a pop up message asking if I want to 'leave page' or 'stay'. I'm not sure what the deal is since I doesn't happen all the time. Perhaps it's on my end? If I choose to remain on the page nothing happens so I have to click the 'leave' button in order to make the post and everything seems to work just fine but it kind of freaks me out.

Anyone have a clue what's going on with this?