I am currently collaborating with the iUI development team on refining the CSS style for our project, and I must admit that I am thoroughly impressed by the capabilities of this compact browser. It is remarkable how most webkit functionalities are accessible to users, including -webkit-gradients, enabling us to create UI elements without relying on images.
Even though it is possible to adjust page rendering based on User-Agent strings, I suggest avoiding this approach and instead utilizing a stylesheet parameter specifically targeting iPhones.
<link media="only screen and (max-device-width: 480px)" href="iPhone.css" type="text/css" rel="stylesheet" />
By employing this method, you can maintain uniform HTML markup while customizing the appearance for iPhone users.
For iPhone OS Emulators provided by Apple, Safari is available on Windows, but remember to change the user agent to iPhone in the developer options. Personally, I prefer using Chrome due to its utilization of the webkit engine, which ensures CSS compatibility.
Typically, individuals engaged in such development work possess an iPod Touch or iPhone. Hence, it is advisable to test on the 2G phone as it offers the strictest limitations and slowest CPU performance. This worst-case scenario testing ensures that if acceptable on the 2G model, the experience will only improve for users with 3G and 3GS models.
Some valuable resources on this topic include:
Apple's Webapps Page
Apple's Developer Safari Page - Includes Link to iPhone Simulator (MAC ONLY).
ADC: Safari Reference Library
ADC SRL: Getting Started with Web Apps
ADC SRL: Getting Started with iPhone Web Apps
Archived: iPhone Human Interface Guidelines for Web Applications - Metrics, Layout Guidelines, and Tips