There are different values of "support". I "support" IE6 and 7 (I make sites for small businesses in the UK), as in, the site works, and the content is accessible. Those browsers make up 0.8% and 4.1% of the traffic last month respectively. (Why the hell is IE7 still used? How do people even have it installed???). For those, I'm happy to strip out sections if needed to get things to work, though this is rarely needed to be honest.
IE8 makes up 11.9%, so we do proper testing there, and the content should look as close as possible to modern browsers, but I'm happy to include polyfills etc where needed.
For us, Chrome is 21.1%, Mobile Safari is 17.5%, IE9 is 17.1%, and Firefox is 15.6%, so for us over 70% of users have a modern browser. These 4 are our target browsers, where everything should work.
While I do at least take a peek at IE7, I usually insert a messages on IE6 & 7 users simply telling them to upgrade their browser rather than debug. The only people who are unable to upgrade their browsers are generally gov't types. Everyone else needs to stop being so lazy and devs need to stop being so accommodating. I still support 8, which let's be honest, is basically as bad as 6 or 7 in a lot of ways but it still the highest version of XP. I know people think XP is enough and they stay there, but they can still go download Firefox or Chrome.
As a concession to old browser users, I will use XHTML or an older spec on a site that has large IE<9 usage. But I'm sure as hell not going to spend a lot of time debugging and fluffing the pages anymore. These people don't care enough about the Internet to not use IE7 or 8, then I don't care if their experience is sub par.
