I’ve started a new project I call the html showcase.
github at http://github.com/xpika/html-showcase
The idea for this is to have page featuring as many html elements and styles on the one page. This will be useful for beginners and also for pros who want speed dial documentation to that rare html tag or style. This should also work as a kind of caniuse test with a real result to show what a html widget or style looks like in said browser.
Happy to accept pull requests.