Mobile devices have screens that are typically smaller and running at a lower resolution that your typical desktop/laptop PC (my laptop is running at 1920x1200), when you open a typical web page the content is designed to be viewed at desktop resolutions, which means that you are using the cursor keys to navigate the page on your mobile device.

Take a look at the DeepFish browser from Microsoft Live Labs.

There's also a cool video over at On10.net

- Mike