(function($) {
	if(!document.defaultView || !document.defaultView.getComputedStyle){
	    var oldCurCSS = jQuery.curCSS;
	    jQuery.curCSS = function(elem, name, force){
	        if(name === 'background-position'){
	            name = 'backgroundPosition';
	        }
	        if(name !== 'backgroundPosition' || !elem.currentStyle || elem.currentStyle[ name ]){
	            return oldCurCSS.apply(this, arguments);
	        }
	        var style = elem.style;
	        if ( !force && style && style[ name ] ){
	            return style[ name ];
	        }
	        return oldCurCSS(elem, 'backgroundPositionX', force) +' '+ oldCurCSS(elem, 'backgroundPositionY', force);
	    };
	}

	var oldAnim = $.fn.animate;
	$.fn.animate = function(prop){
	    if('background-position' in prop){
	        prop.backgroundPosition = prop['background-position'];
	        delete prop['background-position'];
	    }
	    if('backgroundPosition' in prop){
	        prop.backgroundPosition = '('+ prop.backgroundPosition + ')';
	    }
	    return oldAnim.apply(this, arguments);
	};

	function toArray(strg){
	    strg = strg.replace(/left|top/g,'0px');
	    strg = strg.replace(/right|bottom/g,'100%');
	    strg = strg.replace(/([0-9\.]+)(\s|\)|$)/g,"$1px$2");
	    var res = strg.match(/(-?[0-9\.]+)(px|\%|em|pt)\s(-?[0-9\.]+)(px|\%|em|pt)/);
	    return [parseFloat(res[1],10),res[2],parseFloat(res[3],10),res[4]];
	}

	$.fx.step.backgroundPosition = function(fx) {
	    if (!fx.bgPosReady) {
	        var start = $.curCSS(fx.elem,'backgroundPosition');

	        if(!start){//FF2 no inline-style fallback
	            start = '0px 0px';
	        }

	        start = toArray(start);

	        fx.start = [start[0],start[2]];

	        var end = toArray(fx.end);
	        fx.end = [end[0],end[2]];

	        fx.unit = [end[1],end[3]];
	        fx.bgPosReady = true;
	    }

	    var nowPosX = [];
	    nowPosX[0] = ((fx.end[0] - fx.start[0]) * fx.pos) + fx.start[0] + fx.unit[0];
	    nowPosX[1] = ((fx.end[1] - fx.start[1]) * fx.pos) + fx.start[1] + fx.unit[1];
	    fx.elem.style.backgroundPosition = nowPosX[0]+' '+nowPosX[1];
	};
	})(jQuery);