Even Microsoft admits how bad IE6 was. Frankly, they should do the same to versions 7 and 8.
Why is IE6, 7, and 8 bad? Web developers are usually tasked to make sure that website designs and layouts look the same on all browsers. That be easy if all browsers follow rules set by the W3C. All browsers did well, except for IE. What would look the same on Firefox and Chrome would be broken on IE.
The Acid3 test was made to test a browser's compliance with standards. It is a good (although not perfect) way to see if a browser compliant or not.
The video above shows the Acid3 results of Chrome, Opera, Firefox, and IE8. Opera and Chrome scores 100, Firefox scores 94, but IE8 scores only 20. Older versions barely render the page properly. IE9, in comparison, gets a shiny 100.
Almost 25% of users in China still use IE6. With China's economic status, this implies a problem. Web developers will still need to consider IE6 because of the market in China.
If you use a PC with an older version of IE, please tell the owner to upgrade their browers to Chrome, IE9 or Firefox (I'm assuming the PC is not yours.).