Personally I only worry about devices with 320px width or greater. In a sense I don’t care much about smaller devices, although I expect sites I make to have some (possibly reduced) functionality in every browser. Check this for more details Media Queries for Standard Devices
HTML mobile UI Frameworks
Jquery UI tabs css reset style
A unified user interface system across all popular mobile device platforms, built on the rock-solid jQuery and jQuery UI foundation. Its lightweight code is built with progressive enhancement, and has a flexible, easily themeable design.
By popular demand: coded real-world examples of themeable buttons and toolbars using the jQuery UI CSS framework, a system of classes developed for jQuery UI widgets that can easily be applied to any plugin, and even static content.