Internet Explorer 6, released on August 27, 2001, was a package of problems right from the start.

Within a year of release, Microsoft silently declared that IE 6 would not make enough money for them to continue supporting. The result has been numerous security problems, unfixed browser bugs, and a daily migraine for developers.

Six years later, IE 6 is still a thorn in the backside of developers and it's been perfectly clear that IE 6, for the whatever reasons, must die.

Link: http://ie6-must-die.com