Finally Youtube has decided to drop support for the outdated Version 6 of the Internet Explorer, which is still surprisingly often in use (10% - 20% of all internet users). Webdesigners appreciate this step because the Internet Explorer following its own standarts has always been a burden to them. It was often neccesary to do dirty hacks to get a page displaying nice in all common browsers. Besides the Internet Explorer 6 is known to be relatively insecure.
Now with a big services like Youtube (Digg and Twitter may follow soon) turning their back on the Internet Explorer 6, many users are more likely to upgrade to newer versions or even switch to an alternative browser. Youtube suggests their users to switch to Internet Explorer 8, Firefox 3.5 or Googles Chrome 2.