function tree(id) {
 if (document.getElementById(id).style.display == "block") {
    document.getElementById(id).style.display="none";
    document.getElementById(id + "title").style.fontWeight ="normal";
 }
 else {
    document.getElementById(id).style.display="block";
    document.getElementById(id + "title").style.fontWeight ="bold";
 }


}