function popup(url, name, width, height, options)
    {
        var x = (screen.width - width) / 2,
            y = (screen.height - height) / 2
            ;

        options +=	', left=' + x +
            ', top=' + y +
            ', width=' + width +
            ', height=' + height
        ;
        options = options.replace(/^,/, '');

        var win = window.open(url, name, options);
        win.focus();
        return win;
    }
Opens up a centered popup window.
@param {String} url		URL to open in the window.
@param {String} name		Popup name.
@param {int} width		Popup width.
@param {int} height		Popup height.
@param {String} options	window.open() options.
@return {Window}			Returns window instance.