Thanks for your answers so far!
Of course I know that the arduino is kind of underpowered for a whole webserver. But that's not the point. I want to use a little webserver as an interface between a user and the arduino. I just want to access it with my mobile device and want to switch some states (buttons and stuff) and get some values like temperature and stuff. For example: Access webpage on arduino through iphone, press a button to activate sensor measurements and readback, for instance, a temperature value.
For that I want to use jquery because of its universal usage and nice style.