Should you care about the level of HTML5 support in your browser? Maybe not now, but it all depends upon what the content producers do. Most websites don't require any of the new features in the fifth edition of the HTML standard, and most will probably take their time adopting them until they're quite standard. Only the bravest developers will try them first while they're not supported broadly.
[ Find out which of the leading browsers is the perfect balance of features, speed, innovation, and flexibility for you. See "The best Web browser: Chrome, Firefox, Internet Explorer, Opera, or Safari?" ]
The website HTML5test.com does a good job of working through a checklist of HTML5 features to see how many a browser supports. Here are the scores (from 0 to 300) for each of the browsers reviewed. The bonus points are given for extra support of codecs and other options.
|HTML5 Test Score||Bonus Points|
|Firefox 4.0 beta||189||9|
|Internet Explorer 8.0 / 9.0 beta||27 / 84||0 / 1|
The IE scores look quite bad, but this doesn't necessarily indicate that IE is lacking in new features. Microsoft just has its own version. The HTML5 standard embraces Scalable Vector Graphics (SVG) and the Canvas element. Microsoft implemented something called Vector Markup Language (VML) that does pretty much the same thing. But anything that can be undone by petty infighting can be unified with an additional layer of code. Someone has already written an AJAX library to start abstracting away the differences; see ExplorerCanvas.
A simple way to test the memory consumption of the browsers is to load up some big, fat web pages and see how much memory is allocated to the job. This is a fairly good way of simulating the load on the machine, but it's far from perfect. Some browsers may make more use of memory through subprocesses and parts of the operating system. This just counts the memory allocated to processes officially assigned to the named application in the Windows Task Manager.