var browser=0;
    if ((navigator.appName=="Netscape") &&
    (parseInt(navigator.appVersion)>=3)) browser=1;
    if ((navigator.userAgent.indexOf('ozilla')>=0) &&
    (parseInt(navigator.appVersion)>=4)) browser=1;
    var browser2=1;
    if ((navigator.appName=="Netscape") && (parseInt(navigator.appVersion)==3)) browser2=0;

    function ventana(lh) {
    if ((browser==1) && (browser2==1))
    window.open(lh,'lh','toolbar=0,location=0,directories=0,status=0,menubar=0,scrollbars=1,screenX=0,width=640,height=480,screenY=0,left=0,top=0');
    else
    window.open(lh,'lh','toolbar=0,location=0,directories=0,status=0,menubar=0,scrollbars=1,width=640,height=480,resizable=0');
    }