Scott Jehl/Kangax’s fixed positioning test

test.js

$.support.positionFixed = (function (){
	var contain = $( document.documentElement );
		
    if ( 'getBoundingClientRect' in contain[0] ) {
		var el = $( "<div style='position:fixed;top:100px;'>x</div>" ).appendTo( contain ),
			originalHeight = contain[ 0 ].style.height,
			w = window,
			result;

		contain.height( screen.height * 2 + "px" );

		w.scrollTo( 0, 100 );

		result = el[ 0 ].getBoundingClientRect().top === 100;

		contain.height( originalHeight );

		el.remove();

		w.scrollTo( 0, 0 );

		return result;
	}
	return false;
})();