A. D.'s Library tagged mobile →  View Popular

The most important differences are:

• The screen size of the iPhone (320x480) is much smaller than even the smallest target
  application for a desktop Web application. The iPhone screen also has a significantly
  different aspect ratio from a typical desktop or laptop monitor.
• The pixel density of an iPhone is much greater than a desktop
  monitor, allowing small text to be read somewhat more easily and somewhat changing the relative size of images.
• Users can rotate the Mobile Safari view 90 degrees, changing the size and, more importantly, the aspect ratio of the screen.
• The touch-screen interface to Mobile Safari is less precise than a mouse interface,
  meaning that targets like buttons and links should be larger and farther apart than would be necessary in a desktop application.
• An iPhone is often used under slow network conditions. However, users have a strong expectation that the responses to their actions will be nearly instant.

There are two primary options for giving your Web application an iPhone look and feel:

• Add your own CSS and JavaScript to your site based on Apple's sample code or other good-looking sites.
• Use a pre-existing toolkit.

To serve your mobile users, your Rails application needs to manage the
following:

• Detecting when a user accesses the site using an iPhone or an iPod touch.
• Allowing the user to freely switch between the mobile and regular versions of the site.
• Using a different layout for Mobile Safari users, including separate Cascading
  Style Sheets (CSS) files and, possibly, JavaScript libraries.
• Serving different content to mobile users.