Problem solved, thanks everybody
Here's the problem
I have something like this
<a href='http://google.com' class="buy_now" >
<div class='yada yada' > Go </div>
</a>
buy_now has background-color on :hover
In chrome it works In firefox, while hovering, it keeps flashing / blinking etc
Is there anything wrong with my code or this is a firefox bug
Here's the live demo: http://duskblue.org/firefox_bug.html
Edit: ok, seems to be a transitory problem here, works fine after restarting firefox. :/ (3.5.9) here.
Edit 2: demo is now valid HTML according to validator.w3.org