Block IE6 from browsing your website

jReject provides a simple, robjust, light-weight way to display rejections based on a the browser, specific browser version, specific platforms, or rendering engine. Provides full customization of the popup. Uses no CSS file (by default), and can easily be used on page load or during a specific page event. Also provides a flexible way to beautifully and cleanly display custom browser alternatives in the popup.

Using jReject you can block any browser from visiting your website. I would actually never do this. Why turn away anyone from your website just because of their browser preference.

jReject:
http://jreject.turnwheel.com/