function tabbox(sid){
 this.selected=sid;
 this.defaulttab=sid;
}

tabbox.prototype.tabclick = function(tid){
 this.tabgoto(tid);
}

tabbox.prototype.tabgoto = function(tid){
  var tab=document.getElementById('tab-'+tid);
  if (!this.disabled(tab)){
    document.getElementById('tab-'+this.selected).className="tab-button-unsel";
    document.getElementById('tab-content-'+this.selected).className="tab-content-unsel";
    document.getElementById('tab-'+tid).className="tab-button-sel";
    document.getElementById('tab-content-'+tid).className="tab-content-sel";
    this.selected=tid;
  }
}

tabbox.prototype.tabenable = function(tid){
  var tab=document.getElementById('tab-'+tid);
  if (this.disabled(tab)){
    tab.className='tab-button-unsel';
  }
}
tabbox.prototype.tabdisable = function(tid){
  var tab=document.getElementById('tab-'+tid);
  if (tid==this.selected)
   this.tabgoto(this.defaulttab);
  tab.className='tab-button-disabled';
}

tabbox.prototype.disabled = function(tab) {
  return (tab.className == "tab-button-disabled");
}