Note: This is a question about simulating the Browser on the iPhone, not simulating the whole device. I know that iPhone-device simulation is not possible o
[I know the question's quite old now, but maybe my answer might help people coming in with the same query...]
I have found the Google Canary browser's emulator to be one of the best and quickest for testing browser compatibility issues on a windows machine.
It even emulates the iphone's 2x device pixel ratio.
Definitely give it a try and see if it reproduces your issue:
http://www.google.co.in/intl/en/chrome/browser/canary.html
To try out the emulation, hit F12 and below the usual row of dev tools, you will see the second row like in this screenshot...
Plus, it also renders many of the popular device browsers out there...
Hope this helps.