A few weeks ago , i came across a glitch which may catch out you developers who use Firefox a lot for testing your code.
I recently added a ASp.net control to display youtube videos. The links came from a database and the customer hadn't got much content. As a result there were several entries that didnt have links. This worked fine in firefox, but Internet explorer hung whilst trying to download the non-existant video file.
Remember , always test things in both browsers and use default URLS when linking to video or just display something else like a comming soon message.