I use a Microsoft 5-button mouse. It has the two extra buttons on the side that can be configured for BACK and FORWARD (among other things) when you are using your browser.
Today, I accidently backed out of a game because I bumped the side button as I was reaching to grab my mouse. I've done this plenty of times of before and never had it back me out of the game before. Once I bumped it, I was looking at google homepage.
Please disallow the use of the BACK & FORWARD browser functions while playing the game.