Hi Pavel,
Thanks for your answer.
It didn't do the trick. I still have a blank page after deleting the embeded video.
The only way fo the page to load content in my firefox is to delete or disable any Joomla module add-on or other addon containing one (Tabs in this case).
Toufiq, i see you're using a mac, could it make a difference ? I recently had this kind of issue using a css customed horizontal navbar. Didn't show in firefox on a mac as it automatically hides it by defaut in system preferences (and moz doesn't use webkit).