function showTab( T ) {
  i = 0;
  while ( document.getElementById( "tab" + i ) != null ){
    document.getElementById( "div" + i ).style.display = "none";
    document.getElementById( "tab" + i ).className = "";
    document.getElementById( "header" + i ).style.display = "none";
    i++;
  }
  document.getElementById( "div" + T ).style.display = "";
  document.getElementById( "tab" + T ).className = "active";
}