This post is in progress.
Making updates and retrieving data after the initial load needs to be done using ajax. If you try to load another web page from a webapp, the iPhone takes the user into safari.
Apple have good details of the meta tags you can use to customize how iPhone handles your webapp.
This post will contain details specific to getting a webapp to play nice on the iPhone.
- Ajax – http://www.w3schools.com/Ajax/default.asp
- Samples – http://groupaware.mobi/iphone/#_Samples