function makeVisible(pid)
{
	revalidate(pid);
}

function makeInVisible()
{
	document.getElementById("product_div").innerHTML = '';
}

function rePosition(e) {
	var posx = 0;
	var posy = 0;
	if (!e) var e = window.event;
	if (e.pageX || e.pageY) 	{
		posx = e.pageX;
		posy = e.pageY;
	}
	else if (e.clientX || e.clientY) 	{
		posx = e.clientX + document.body.scrollLeft
			+ document.documentElement.scrollLeft;
		posy = e.clientY + document.body.scrollTop
			+ document.documentElement.scrollTop;
	}

	// posx and posy contain the mouse position relative to the document
	// Do something with this information
	if( typeof( window.pageYOffset ) == 'number' ) {
    	//Netscape compliant
		scrOfY = window.pageYOffset;
		scrOfX = window.pageXOffset;
	} else if( document.body && ( document.body.scrollLeft || document.body.scrollTop ) ) {
		//DOM compliant
		scrOfY = document.body.scrollTop;
		scrOfX = document.body.scrollLeft;
	} else if( document.documentElement && ( document.documentElement.scrollLeft || document.documentElement.scrollTop ) ) {
		//IE6 standards compliant mode
		scrOfY = document.documentElement.scrollTop;
		scrOfX = document.documentElement.scrollLeft;
	}

	if (scrOfY > 200)
	{
		document.getElementById("product_div").style.top = scrOfY;
	} else {
		document.getElementById("product_div").style.top = 200;
	}	

	if( typeof( window.innerWidth ) == 'number' ) {
    	//Non-IE
    	myWidth = window.innerWidth;
    	myHeight = window.innerHeight;
	} else if( document.documentElement && ( document.documentElement.clientWidth || document.documentElement.clientHeight ) ) {
		//IE 6+ in 'standards compliant mode'
		myWidth = document.documentElement.clientWidth;
		myHeight = document.documentElement.clientHeight;
	} else if( document.body && ( document.body.clientWidth || document.body.clientHeight ) ) {
		//IE 4 compatible
		myWidth = document.body.clientWidth;
		myHeight = document.body.clientHeight;
	}
/*
	if (posx <= myWidth/2)
	{
		document.getElementById("product_div").style.left = posx + 50;
	} else {
		document.getElementById("product_div").style.left = posx - 450;
	}
*/
}

<!--AJAX-->
function recreateRequestObject() {
    var ro = null;
    var browser = navigator.appName;
    if(browser == "Microsoft Internet Explorer"){
        ro = new ActiveXObject("Microsoft.XMLHTTP");
    }else{
        ro = new XMLHttpRequest();
    }
    return ro;
}

var http = recreateRequestObject();
var trigger;
var division;
var div;

function revalidate(id)
{
	var url;
    url = '/nc7/cards/card.php?c='+id;

	if (document.captureEvents) document.captureEvents(Event.MOUSEOVER);
	document.onmouseover = rePosition;

    http.open('get', url, false);
    http.onreadystatechange = rehandleResponse;
    http.send(null);

	div = "product_div";

    if(http.status == 200)
    {
        var response = http.responseText;
		document.getElementById(div).innerHTML = response;
    }
}

function rehandleResponse()
{
    if(http.readyState == 4)
    {
        var response = http.responseText;
    }
}
<!--END AJAX-->