UPDATE: this post is for Jan 2012, click here for the Feb 2012 report.
HTML5 / CSS3 development for mobile browsers needs to be aware of the reported screen size to effectively build a mobile site.
The iPhone and iPad are consistent and predictable. All iPhones report a window size of 320 x 460, and all iPads report a window size of 768 x 1004.
Here are the most common reported screen sizes for Android devices (in Portrait orientation):
320 px width – 90% of devices queried
360 px width – 10% of devices queried
800 px width – 1 device reporting (insufficient data)
Using this information, you can more easily develop your CSS media queries, knowing what sizes your app is likely to encounter in the wild.
This will be an ongoing monthly report, and will reflect different reported window sizes when new devices are introduced. By regularly reporting this information, a trend over time can be identified.
UPDATE FEB 1st: final numbers for January 2012 included