This is really cool. The World Wide Web Consortium (W3C) Mobile Web Initiative (MWI) has just release as Web Compatibility Test for Mobile Browsers. It tests against compatibility with twelve different Web technologies.
Point your phone’s browser to: http://dev.w3.org/2008/mobile-test/test.html.
If you see twelve green boxes, your mobile browser has passed the test.
Here’s hoping that this compatibility test will cause the same level of competition among mobile browser vendors as the release of Acid 3 did for desktop browser vendors.
Oatmeal Stout - Justin Thorp's blog 
It didn’t fully like the iPhone. 😦
Great post Justin! As the mobile web matures, it definitely needs to start laying out some cross-browser standards.
Also, here’s the tinyurl link to their mobile test for easier thumb-typing: http://tinyurl.com/37e33p