The issue is that Microsoft will not give access to the API's on ARM systems that are required to do this. http://weblogs.mozillazine.org/asa/archives/2012/05/

The issue is that Microsoft will not give access to the API's on ARM systems that are required to do this. http://weblogs.mozillazine.org/asa/archives/2012/05/firefox-on-windows-o.html http://weblogs.mozillazine.org/asa/archives/2012/05/firefox-... "Here's what's going on. For Windows on X86, Microsoft is giving other browsers basically the same privileges it gives IE. It's not great that you don't get those privileges (certain API access) unless you're the default browser and I think that's deeply unfair (a post for later,) but at least we're able to build a competitive browser and ship it to Windows users on x86 chips. But on ARM chips, Microsoft gives IE access special APIs absolutely necessary for building a modern browser that it won't give to other browsers so there's no way another browser can possibly compete with IE in terms of features or performance. This is in direct violation of the promises they made to developers, users, and OEMs about browser choice in documents which mysteriously disappeared from Microsoft's site -- remember this? I sure do."