And if they can't upgrade, or won't, or don't want to, or don't trust you to tell them to install something? We went through this years ago with IE6, there wer

And if they can't upgrade, or won't, or don't want to, or don't trust you to tell them to install something? We went through this years ago with IE6, there were always plenty of devs with variations of "screw 'em", but blaming or penalising users for their set up is a bit of a dick move, and shutting out or inconveniencing a big chunk of potential market is not a good business strategy. There does come a point where the cost of supporting a browser exceeds the value of the people using it, but I'd be surprised if most sites have hit that for IE8 (the third most used browser, more than twice the market share of the most used firefox).