iPad css orientation

Question

Hi guys, i want to test the orientation by using css for ipad.This is the css file i use

@media only screen and (device-width:768px) and(orientation:portrait) { body { background: green; } }

@media only screen and (device-width:768px) and(orientation:landscape) { body { background: red; } }

I am not sure whether this will work or not. I tried testing in an iphone emulator by changing the device width to 320px.But it didn't work. Do i need to change anything in this css file? This is how i call the css in the main page

"link rel="stylesheet" type="text/css" href="iPad.css" />"