Microsoft announced the final release of Internet Explorer 9 yesterday, so I think it's time to explain why I don't support older versions of IE (mainly 7 and 6). The reason is simple: supporting older versions of IE is harmful for IE's users. Why? There are two reasons behind this. First, if you support these browsers, you're actually encouraging their users to continue with their bad habits and this is harmful for their computer security. Using an obsolete browser exposes users to malicious attacks that can compromise the integrity of their data. So if you build a web site that fully works in IE 6 and 7, you're indirectly contributing to the massive widespread of malware infections, phishing hoaxes and similar security problems. An obsolete browser is affected by several bugs that may harm a user's computer. Every site that still supports these browsers convinces IE's users that there is no need to upgrade their browsers. If you do that, be aware of the potential danger of what you're doing.
Second, if you still support these browsers, you're actually preventing the latest releases of Internet Explorer (8 and 9) from being adopted by the majority of web users. Microsoft has put so much effort in the development of IE that it would be harmful even to Microsoft if you continue with supporting obsolete versions of IE. The intention of IE 9 and 8 is to provide web developers and users with a full standard-compliant web browser. If you don't drop your support to older versions of IE, you're actually frustrating the hopes of Microsoft, web developers and simple users in a better web.
Please don't do that. Please stop supporting IE 6 and 7! smile