jQuery.fn.offset can be more simplify.

parseInt is not necessary.

it can change to...

jQuery.fn.offset = function() {
	var elem = this[0];
  if ( !elem ) return { top: 0, left: 0 };
  var doc = elem.ownerDocument, body = doc.body;
	if ( elem === body ) return jQuery.offset.bodyOffset( elem );
	if ( document.documentElement["getBoundingClientRect"] ){
		var box  = elem.getBoundingClientRect(), docElem = doc.documentElement,
			clientTop = docElem.clientTop || body.clientTop || 0, clientLeft = docElem.clientLeft || body.clientLeft || 0,
			top  = box.top  + (self.pageYOffset || jQuery.boxModel && docElem.scrollTop  || body.scrollTop ) - clientTop,
			left = box.left + (self.pageXOffset || jQuery.boxModel && docElem.scrollLeft || body.scrollLeft) - clientLeft;
	}else{
		jQuery.offset.initialized || jQuery.offset.initialize();

		var offsetParent = elem.offsetParent, prevOffsetParent = elem,
			doc = elem.ownerDocument, computedStyle, docElem = doc.documentElement,
			body = doc.body, defaultView = doc.defaultView,
			prevComputedStyle = defaultView.getComputedStyle(elem, null),
			top = elem.offsetTop, left = elem.offsetLeft;

		while ( (elem = elem.parentNode) && elem !== body && elem !== docElem ) {
			computedStyle = defaultView.getComputedStyle(elem, null);
			top -= elem.scrollTop, left -= elem.scrollLeft;
			if ( elem === offsetParent ) {
				top += elem.offsetTop, left += elem.offsetLeft;
				if ( jQuery.offset.doesNotAddBorder && !(jQuery.offset.doesAddBorderForTableAndCells && /^t(able|d|h)$/i.test(elem.tagName)) )
					top  += ( computedStyle.borderTopWidth - 0 ) || 0,
					left += ( computedStyle.borderLeftWidth - 0 ) || 0;
				prevOffsetParent = offsetParent, offsetParent = elem.offsetParent;
			}
			if ( jQuery.offset.subtractsBorderForOverflowNotVisible && computedStyle.overflow !== "visible" )
				top  += ( computedStyle.borderTopWidth - 0 ) || 0,
				left += ( computedStyle.borderLeftWidth - 0 ) || 0;
			prevComputedStyle = computedStyle;
		}

		if ( prevComputedStyle.position === "relative" || prevComputedStyle.position === "static" )
			top  += body.offsetTop,
			left += body.offsetLeft;

		else if ( prevComputedStyle.position === "fixed" )
			top  += Math.max(docElem.scrollTop, body.scrollTop),
			left += Math.max(docElem.scrollLeft, body.scrollLeft);

	}
	return { top: top, left: left };
};