Priority Inbox for desk/laptop Gmail was a smash hit when it was launched last summer, and the product has transformed the way millions of people organize and think about their email, including me. For those of you who haven’t tried Priority inbox, the idea is simple: Gmail can predict which emails will be most important to you and raise them to the top of your inbox in their own category. It does this is the same way that it does with spam, and can improve accuracy by learning your habits over time; who you read emails from, keywords that usually result in a response, etc. You can also manually tag and untag priority messages to speed up the process. Priority Inbox was a serious upgrade to the standard Gmail client, and it is now available in the HTML5 web app.
Gadgets running iOS 3.0+ and Android 1.5+ can now access a fully functional Priority Inbox simply by visiting m.gmail.com. Because the Android Gmail Market app recently received much better Priority Inbox support, this new web app feature is beneficial primarily to iOS users.
Via the Gmail Blog