var MAX_LINES = 12;
  var begin = '<ul><li>';
  var middle = '</li><li>';
  var end = '</li></ul>';
  
  function trace(msg) {
          var output_window = document.getElementById("trace");
          var lines = output_window.innerHTML.toLowerCase();
          var lineList;
          
          if (lines.length > 0) {
                  lineList = lines.substring(begin.length, lines.length - end.length).split(middle);
                  while (lineList.length >= MAX_LINES) { lineList.shift(); }
                  lineList.push(msg);
          }
          else {
                  lineList = [ msg ];
          }
          
          output_window.innerHTML = begin +lineList.join(middle) +end;
  }