winMain = null;

function startup() {
    winMain=window.open("navi.html","main","width=800,height=583,toolbar=no,status=no,resizable=no,menubar=no,location=no,left=20,top=20");
    window.setTimeout("checkPopup()",500);
}

function checkPopup() {
    var reopener = document.getElementById("reopener");
    var popwarn  = document.getElementById("warnpopup");

    if (winMain == null) {
        if (reopener) {
            reopener.style.display="none";
        }
        if (popwarn) {
            popwarn.style.display="block";
        }
    } else {
        if (reopener) {
            reopener.style.display="block";
        }
        if (popwarn) {
            popwarn.style.display="none";
        }
        winMain.focus();
    }
}