| Here's the thing, I'm no expert on this, but isn't this website and browser related? I mean, if you're making a browser game, you'd usually have it at a fixed resolution or in fullscreen. If I remember right, there were some posts a while ago talking about toggling fullscreen. But as for the resizing thing, don't most browsers already handle this? Not properly mind you, but I remember being able to just resize the console in the test HTML file, and having it stretch the canvas proportionally (It'll just resize; the resolution of the canvas won't be changed). After testing this, I can confirm this to be the case.|
I was going to post an example of this, but this thread should help you out, at least somewhat. I make no guarantees that it will work for you. Also note that the example nikoniko posted is using Diddy (At the bottom of the thread). You'll likely need to modify that example.
There's also some posts in the HTML5 section you can look through.