function openCenteredWindow(url, name, width, height) {
    var configString = 'width=' + width + ',height=' + height + ',status=1';
    newWindow = window.open(url, name, config=configString);
    if (parseInt(navigator.appVersion) >= 4) {
        var screenWidth = screen.width;
        var screenHeight = screen.height;
        var x = (screenWidth - width) / 2;
        var y = (screenHeight - height) / 2;
        newWindow.moveTo(x,y);
    }
}