I couldn't think of a better title for this question, but please don't jump to conclusions - I don't really want to point a gun at my users heads!
I have a site that works well with the modern browsers like IE9+, FF12+, or Chrome. Due to the lack of HTML5 support (specifically some canvas related issues) the site doesn't work in older browsers, like IE8, for example.
The site is a part of a prepaid service, the users are warned about these constrictions before they pay, and yet there still are users that buy the service while having these old browsers on their computers.
From one side to support those means to fully recreate the site in Flash or Java, for example. That means lots of work for a relatively small (up to 15%) percent of my target audience.
From the other side I don't want to "disappoint" them by bluntly stating "Your browser is too old", I want to give them an interesting feedback, visually and/or verbally, that will make them really want to upgrade. The best idea I come with is to show them the video of the working site, but it seems too heavy and boring.
Any suggestions? Thanks.
It seems from a short user survey that I did, that users definitely prefer to install a plugin and not to upgrade. Therefore I am going to accept the Chrome Frame answer.
I want to thank you all for a very interesting discussion, I have learned a lot and got a lot of inspiration from it.