If you want to try out WebSockets or IndexedDB then Microsoft has prepared a play room where you can't do any harm and can't delude yourself into thinking that you are creating production code.
Microsoft has launched a web site that you can use to test HTML5 apps. The facilities incorporated in the lab aren't in IE 9 but are prototypes for standards that might well make their way to the production browser when the standards settle down. Essentially the lab is all about providing an early experience of standards that are incomplete at the moment and might well have to change.
At the moment the only two prototype technologies in the lab are WebSockets and IndexedDB. Of the two you might be most surprised that WebSockets is considered to be unstable. The simple fact it that while it has been included in the standard raft of HTML5 technologies it is far from complete as a specification and what is currently recognised as WebSockets is going to have to changed before it reaches the final version and the changes are going to be big enough to break anything you might have implemented using the pre-standard version.
The site comes with the following cautionary note:
WARNING: These specifications are unstable and will change. Developer code and web pages based on these specifications will break and will have to be re-written. Use these prototypes only to experiment with new HTML5 features and not for production code.
Rather than include these unstable standards in IE9 and hence encourage programmers to think that they are stable enough to code against Microsoft has separated them out into a "play area" where we can gain experience of each standard without making the mistaken commitment to creating production code.
This all seems like a good idea and perhaps one that other browser creators should try. It is probably too much to hope that they might get together and provide a single HTML5 standards lab that we can use to try things out on a range of browsers.
HTML5 - I've seen it. It's rubbish.
Pro HTML5 Programming (Book Review)
Introducing HTML 5 (Book Review)