@Naji IE does not support webGL or the gamepad API as well as many other issues. You will also find performance issues in number of sprites, sound, etc... IE is my browser of choice but if you actually want to make more complex games you really can't just target IE. I use it as the lowest common denominator for perf though. But as already stated, if you want to reach the widest audience, you cant just target one browser, you need to make sure it works in all of them. Your scenario of an issue in another browser that works fine in IE is rare and most times you will find the opposite. You can't really advise everyone who has much more experience debugging browser issues across multiple browsers that IE is all they should target.