From the Wikimedia Blog:
This week you’ll see some changes to the look and feel of Wikipedia on your phone, as the mobile team moves features that were tested on our experimental Beta site onto our mobile gateway. The updated mobile site will include a navigation system that makes it easier to explore our content, as well as visual improvements aimed at increasing the readability of articles.
The new navigation system is designed to make mobile features and settings more discoverable, paving the way for the addition of new features. In the coming months, the mobile team will continue to experiment with and build contributory features. Whether it’s uploading a photo (as with the Wiki Loves Monuments Android app), watching changes to articles, or even editing, we want anyone to be able to pitch in and help make Wikipedia even better.
If you’re just browsing articles, the first thing you’ll notice is the change to layout and typography. We chose these new fonts for improved device compatibility, ease of scannability and reading, and, more generally, to better fit the high quality standards to which all Wikimedia projects strive2 Our designers will continue to focus on typography going forward, since text is the primary way readers and editors interact with the site.
Improving how we serve content on the mobile web is crucial for reaching our goal of 4 billion pageviews per month by June 2013, and for providing Wikipedia to more readers in countries where mobile is the primary form of Internet access.
Direct to Wikipedia Mobile