If you're going to be designing layouts with fixed size screens for different mobile devices, you may want to mirror that design when running your app on a desktop. The following method fixes the size of the window OUTSIDE of PhoneGap, giving a fixed-sized window on the desktop. Sometimes it's easiest to manage user's expectations and UI design by limiting options!
// create a window of a specific size
var w=window.open('','', 'width=100,height=100');
w.resizeTo(500,500);
// prevent window resize
var size = [window.width,window.height]; //public variable
$(window).resize(function(){
window.resizeTo(size[0],size[1]);
});