From a technical point of view, it's pretty hard to catch up with established competitors especially when they are very good. Though they did catch up in some a

From a technical point of view, it's pretty hard to catch up with established competitors especially when they are very good. Though they did catch up in some areas, they also omitted many features and spec implementations that their competitors have already done, and giving the excuse that they did it because those specs weren't ready enough. But if you really want to know why hasn't Microsoft pushed the development of IE more over the years, I'd say it's politics. The Windows OS thrives because of native software, and most of the native software works only on Windows. So from their point of view, it's not a very good idea to help push the web forward to make (web) apps cross-platform. The reason why they might've changed their mind a bit lately, is because they also have cloud offerings now, and they'd rather have enterprise (mostly) customers continue to use IE instead of moving to a competitor's browser. But it seems they still don't really want to go fully cross-platform. This is not obvious yet, but I think we'll see it with IE10, where they want to tie the hardware acceleration to the Windows OS. That's why they've started marketing the idea of "native HTML5" lately, which basically means HTML5 that is hardware accelerated through DirectX, which of course works only on Windows. All their competitors have adopted WebGL for 3D content, but they'll probably try to promote their DirectX and Windows-only solution, instead.