If you worked on web software at that time, 50% of the work was making something that worked in every other browser, then the next 50% was making it work in IE6 without breaking everything else. The arrival of IE8, while it was less awful than IE6, made things worse because many of the hacks used to make things IE6 friendly, worked with IE8, so the collection of stupid CSS hacks one had to memorize grew even more complex.

IE6 was a browser of the same era as Netscape 4, when it was common and unsurprising for a CSS error or a malformed bit of HTML to crash the browser.

Yeah, I worked on a much smaller product and we aggressively ran automated selenium tests against our whole product with IE6. Sometimes we hit crashes in the browser and I helped people debug them using windbg and find string locals on the stack so we could identify the bad code.

The idea that YT or any other Google product team would justify not CIing against IE6 or Firefox is absurd to me.