var currentDiv=null;
    function show_div(thediv) {
    var div = document.getElementById(thediv);
    hide_div(currentDiv);
    if (div != null) {
    div.style.visibility='visible';
    div.style.display='block';
    }
    currentDiv=thediv;
    }
    function hide_div(thediv) {
    var e = document.getElementById(thediv);
    if (e!=null) {
    e.style.visibility='hidden';
    e.style.display='none';
    }
    }