I have recently built a template for a website that I see looks very different in different versions of Internet Explorer. I was wondering, as a rule of thumb, which versions of Internet Explorer are worth supporting? IE6 and up? IE7 and up?
Wikipedia has a list of resources that provide browser usage statistics that can be helpful in determining the user loss by not supporting certain browsers. The top ones are:
Once your site is up and running, though, you should use analytics software, such as Google Analytics, to gather statistics on what browsers visitors to your site are using so you can gauge how many users you'll be losing by not supporting certain browsers.
Even MS is trying to forget about IE6. http://ie6countdown.com/
This depends massively on the site you're making. A major bank's website needs to work in IE6. Twitter.com doesn't. If you're building a corporate intranet, some companies are stuck on IE6 for legacy reasons. There are huge numbers of variables like this.
Our rule of thumb tends to be "it should look good in IE7+, and be at least functional in IE6" for our projects, but it varies based on the client.
Your audience will not be comparing the site in IE6 and Chrome, anyone stuck with IE 5.5/6.0 is already in for a world of pain in the web and will expect nothing less.
Here is a great site helping with browser states. I selected IE for the link: