IE development was effectively stopped at 2001. After IE6 shipped with XP, IE team was transformed into Avalon project (which, after years of struggle, became WPF). Only IE Sustained Engineering team continued to work on IE6. After some time it became apparent that security challenges are too hard for such a small team and larger effort is required to fix reemerging security issues, so new IE team was created to concentrate on security issues. Some old-timers were transferred from Avalon to found (refound?:) this team.<p>Couple years later it became clear that Firefox is becoming superior browser and Microsoft needs get back into the game. IE7 was announced and current IE team was expanded to meet the challenge. More old-timers left Avalon to join IE7. Then this team shipped IE7, IE8 and (as you would expect) is working on IE9 now.