As recently as 2010, the percent of MP page views coming from mobile phones was negligible. Now it's up to 20% and growing fast, despite the fact that the site is borderline unusable on the tiny screens.
We've changed most (but not all) pages so that they are at least a bit easier to use on a phone screen. It's a hybrid "responsive design" that should keep pages looking normal on a computer, but less squashed on a phone. Pages should also load faster (though we're talking about half a second or so). This required major changes to our 8-year-old layout code, and I expect there will be many formatting bugs!
If you see a problem, please report it here, along with the device type (Windows/Mac computer, iOS, Android) AND the browser (Firefox, Chrome, IE, etc), and a screenshot of the problem if possible.