Ah it seems IE9 is the problem, it works for me in chrome.
From a purely technical standpoint (ignoring art assets) the game is pretty fun. Good job.
The fact that you respawn so quickly after dieing is really good in a game like this. And some of those stages.... Stage 5 is insane - by far the hardest level in the game! I died maybe 50-60 times by the end of my playthrough.
A couple of questions : Was the way your player interacts with moving platforms intended? Because if not hunt the forums you will find some workarounds to be able to jump properly.
Why after every 5 stages do you have the player returning to the menu screen? The main menu button is ever present throughout the whole game - so you can get back there whenever you want! This breaks the flow of the game in my opinion and confuses the player.
If you are dead set on keeping that mechanic then i would suggest adding ticks or crosses through the stages the player completed so progress can be tracked.
With some good graphics we could have another meatboy on our hands.