Are the same methods used to write CSS only for iPhone in landscape mode?
You could do this
<meta name="viewport" content="width=device-width,
minimum-scale=1.0, maximum-scale=1.0">
That forces the iPhone to render viewport the same as the device width.
Then use this css to target the landscape mode, which is +320px
wide
@media screen and (min-width: 321px){
//styles
}