function toggleOverlay(cid) {
    el = document.getElementById("overlay"+cid);        
    el.style.visibility = (el.style.visibility == "visible") ? "hidden" : "visible";    
	
    //alert(el.style.visibility);
	if (el.style.visibility == "visible") {
        changeOpacity(70, "overlay");        
    } else {
        resetOpacity("overlay");    
    }
}

function changeOpacity(opacity, id) {
    var object = document.getElementById(id).style;
    object.visibility = "visible";
    object.opacity = (opacity / 100);
    object.MozOpacity = (opacity / 100);
    object.KhtmlOpacity = (opacity / 100);
    object.filter = "alpha(opacity=" + opacity + ")";
} 

function resetOpacity(id) {
    var object = document.getElementById(id).style;
    object.visibility = "hidden";    
    object.opacity = 0;
    object.MozOpacity = 0;
    object.KhtmlOpacity = 0;
    object.filter = "alpha(opacity=0)";
}