HTML5 goes beyond just the <video>, <audio> or the <canvas> tags. And there's more to it than just the big technical features, drag and drop, filesystem support. What makes it really useful are the little things.
For example, HTML5 context menus which enable a web app to request that the browser add one or more custom entries to the right-click menu.
However, as with many other HTML5 specifications, most browsers don't support custom context menus.
In fact, Mozilla is the only one to add support and this just happened in the recently launched Firefox 8. At this time, Firefox is the only browser to support the feature.
"One of these parts of the specs are context menus, or 'right click menus.' Using HTML5 and a menu element you can add new options to these without having to write a browser add-on," he said.
Since this is such a new feature, you're probably not going to encounter it on the web any time soon. But if you're running Firefox 8 or a newer version, you can check out the demo
page Mozilla has set up to see the functionality in action.
And, if you're a developer, Mozilla is also providing all of the code
necessary to create your own custom menus. Since this is a standard HTML feature, actually creating menu entries is quite simple.
As for why you'd want custom context menu entries, the possibilities are endless.
Just imagine all of the things you can do with a context menu in a desktop app and then remember how many times you right-clicked in a web app, like Grooveshark, expecting to see a context menu relevant to the item you selected. Of course, there's also the risk that the feature will be abused.