browserName = navigator.appName;
browserVer = parseInt(navigator.appVersion);

function pop (url, id, width, height)
{
        var viewerpop = window.open (url, id, 'location=no,toolbar=no,directories=no,menubar=no,resizable=yes,scrollbars=no,status=no,width='+width+', height='+height+', top=50, left=50');
                if ( browserName == "Netscape" && browserVer >= 3 )
        viewerpop.focus();
}