Is your (mobile) browser ready for the Web? The W3C “Mobile Web Test Suites Working Group” has been working on a Web Compatibility Test for Mobile Browsers that tests technologies they expect to be relevant in the next two years or so. The test is in spirit similar to the Acid tests, though it contains tests for features that are already widely supported, but are still in draft status from a specification perspective. Think of XMLHttpRequest, the HTML canvas element, Media Queries, Selectors, contenteditable, et cetera.
As mentioned in their blog post, they are also still accepting test input from everyone who’d like to write a test. So if you didn’t get your pet bug/feature in Acid3, now might be the time.