Take the 2-minute tour ×  Starting with Internet Explorer 8,
Microsoft provided built-in developer tools for Internet
Explorer. IE8 provides IE8 Standards, IE8 Compatibility View,
IE7, and Quirks Mode. IE9 provides IE9 Standards, IE9
Compatibility View, IE8, IE7, and Quirks Mode.  I have often
wondered why Microsoft choose to provide IE6 testing VMs instead
of offering it as a convenient browser mode, while still
providing Quirks Mode. Nobody wants to fire up a VM (now or
three years ago) just to test a random IE6 report, so why did
Microsoft choose to make IE6 testing so difficult for IE7 and
every version following? Has Microsoft ever commented on that
decision?  EDIT: I know IE6 should be avoided and Microsoft
wants to wipe it out for good as a browser. My question is
looking for historical significance. I am wondering if Microsoft
ever publicly announced that IE6 would never be supported by
developer tools from IE8 on, which was released at a time that
IE6's market share was still significant to developer