It's mainly the people that were still using IE6 that MS was targeting (a surprising amount of people are still using it too because it's the version that comes with windowsXP)
IE6 was released in 2001
IE7 in 2006
IE8 in 2009
But it's still a wise idea to keep your browser fully updated even if you had IE8 as a browser is the main "doorway" for infections to find their way onto your computer.