I'm clicking through the internet and start being confused a little bit about if the mobile Safari Brwoser is HTML5-capable now or not. I wanted to open the webqr-Site on my safari Browser on iPod Touch 3rd Gen with the newest iOS and they say, I have to open this site with a browser being capable of HTML5. But actually the mobile safari browser should support HTML5, (Link1, Link2). I'm not into HTML5, that's why I get confused. Does that mean, that the mobile Safari browser started being compatible to some Tags of HTML5, but still not supports the whole functionality? Is there any reliable source for that? I need this information for my thesis.
Mobile Safari is HTML5 capable since v1.0, so since 2007. The exact implementation details for various specs changed over time obviously.
At the moment there is no browser on the planet supporting everything mentioned in the HTML5 spec. That's because it's a working draft, not a finalized specification.
There're a lot of components forming what we call HTML5 and the site you're mentioning needs a specific feature which Mobile Safari doesn't support. So the error message is a bit misleading and user unfriendly. You can see an overview about support for all HTML5 features here.