Having worked on IE back in the day, I can take a good guess as to why XP isn't supported. (I haven't had the time to read all of the reddit responses yet). I

Having worked on IE back in the day, I can take a good guess as to why XP isn't supported. (I haven't had the time to read all of the reddit responses yet). It comes down to cost. Microsoft tests everything way way more than is apparent from the outside. Adding XP support (backporting some version of software D2D) is probably not that difficult from an engineering perspective, but the ongoing test cost is significant. That functionality/cost tradeoff is largely out of the engineering teams hands. The chain of 'whys' probably goes like this: Q: Why can't they do XP? A: Because D2D isn't on XP and because of test cost. Q: Why is test so expensive? A: They have to test the hell out of it and XP increases the matrix. Q: Why so much testing? A: Because of long release cycles means you only have one chance to get it right. Q: Why long release cycles? A: IE is part of Windows and OEMs and Enterprises want long lead times to qualify software. Q: Why is IE part of windows and not disjoint like all other browsers? A: IE has to roll up to some P&L in Microsoft and the mission is to make Windows a more compelling platform. BTW -- Safari 5 doesn't run on Mac OS X 10.4...