function GetID(id) { return document.getElementById(id); } 
function montrerFenetre(src,id_div,id_img) {
    var overlay = GetID('overlay');
    overlay.style.visibility = "visible";

	var my_image = GetID(id_img);
	my_image.src = src;
	
	var my_window = GetID(id_div);
	my_window.style.visibility = "visible";
}

function cacherFenetre(id_div) {
    var overlay = GetID('overlay');
    overlay.style.visibility = "hidden";

	var my_window = GetID(id_div);
	my_window.style.visibility = "hidden";
}

function imgSwap(oImg)  {
   var strOver  = "_on";    // image to be used with mouse over
   var strOff = "_off";     // normal image
   var strImg = oImg.src;
   if (strImg.indexOf(strOver) != -1) oImg.src = strImg.replace(strOver,strOff);
     else oImg.src = strImg.replace(strOff,strOver);
}