function getDocHeight() {
    var D = document;
    return Math.max(
        Math.max(D.body.scrollHeight, D.documentElement.scrollHeight),
        Math.max(D.body.offsetHeight, D.documentElement.offsetHeight),
        Math.max(D.body.clientHeight, D.documentElement.clientHeight)
    );
}

function bigProductMover(){

    var div = document.getElementById("BigProduct")
	var docHeight = getDocHeight()
	var topOffset = 150
    div.style.top = 0;
	
    window.onscroll = function(){
	
		var pageOffset = window.pageYOffset
		if (!pageOffset) 		pageOffset = document.body.scrollTop;
		else if (!pageOffset) 	pageOffset = document.documentElement.scrollTop;

		if (docHeight < pageOffset + div.offsetHeight*1.5) 	targetPos = docHeight - div.offsetHeight*1.5-topOffset;
		else if (pageOffset<topOffset) 						targetPos = 0;
		else 												targetPos = pageOffset - topOffset;
		
        mover()
    }
    
    mover = function(){
    
		var timer
    	var currentPos = parseFloat(div.style.top)
		
		div.style.top = currentPos + (targetPos - currentPos) / 20 + "px";
		
        if (!(currentPos + 5 > targetPos && currentPos - 5 < targetPos)) timer = setTimeout("mover()", 10);
        else clearTimeout(timer);
    }   
}