this is a problem on my 13" screen - the height is smaller than iphone 4.

When I choose iphone 4 the width is correct but height is 'trunctated' making it not render within the right specs.

Maybe ask/inform the user something like:

"You desktop resolution (1024x768) is smaller than what <selected device and rotation name> needs (640x1024).
Do you want to continue using this device ?"

any better suggestion?