//send large image id and thumbnail id as paramaters and
//this function will set the css settings on the large picture and
//it will set up the events for both the large picture and the thumbnail.

function setImageHoverEvents(imageId, imageThumbId) {
    var image = document.getElementById(imageId);
    var imageThumb = document.getElementById(imageThumbId);
    image.style.visibility = "hidden";
    image.style.position = "absolute";
    image.style.left = 200 + "px";
    image.style.top = 200 + "px";
    image.onmouseover = function() { image.style.visibility = "visible"; };
    image.onmouseout = function() { image.style.visibility = "hidden"; };
    imageThumb.onmouseover = image.onmouseover;
    imageThumb.onmouseout = image.onmouseout;
}