new .offset()

gistfile1.js

jQuery.fn.offset = function( options ) {
	if ( arguments.length ) {
		return options === undefined ?
			this :
			this.each(function( i ) {
				jQuery.offset.setOffset( this, options, i );
			});
	}

	var docElem, body, win, clientTop, clientLeft, scrollTop, scrollLeft,
		box = { top: 0, left: 0 },
		elem = this[ 0 ],
		doc = elem && elem.ownerDocument;

	if ( !doc ) {
		return;
	}

	if ( (body = doc.body) === elem ) {
		return jQuery.offset.bodyOffset( elem );
	}

	docElem = doc.documentElement;

	// Make sure it's not a disconnected DOM node
	if ( !jQuery.contains( docElem, elem ) ) {
		return box;
	}

	// If we don't have gBCR, just use 0,0 rather than error
	// BlackBerry 5, iOS 3 (original iPhone)
	if ( typeof elem.getBoundingClientRect !== "undefined" ) {
		box = elem.getBoundingClientRect();
	}
	win = getWindow( doc );
	clientTop  = docElem.clientTop  || body.clientTop  || 0;
	clientLeft = docElem.clientLeft || body.clientLeft || 0;
	scrollTop  = win.pageYOffset || docElem.scrollTop;
	scrollLeft = win.pageXOffset || docElem.scrollLeft;
	return {
		top: box.top  + scrollTop  - clientTop,
		left: box.left + scrollLeft - clientLeft
	};
};