function overlayerAltZoom(blockId) {
    document.getElementById('overlayAltZoom_' + blockId).style.visibility = 'visible';
}
function offerlayAltZoom(blockId) {
    document.getElementById('overlayAltZoom_' + blockId).style.visibility = 'hidden';
}

// generalized functions
function showOverlay(overlayId) {
    try {
        document.getElementById(overlayId).style.visibility = 'visible';    
    }
    catch(e) {
        return false;
    }
}

function hideOverlay(overlayId) {
    try {
        document.getElementById(overlayId).style.visibility = 'hidden';    
    }
    catch(e) {
        return false;
    }
}

function stop_hideOverlay(overlayId, movieName) {
    try {
        stopVideo(movieName);
        document.getElementById(overlayId).style.visibility = 'hidden';
    }
    catch (e) {
        return false;
    }
}
	
function stopVideo(movieName) {
    thisMovie(movieName).stopVideo();
}

function thisMovie(movieName) {
//    if (navigator.appName.indexOf("Microsoft") != -1) {
//        return window[movieName];
//    }
//    else {
        return document[movieName];
//    }
}