function toggleTab(thisTab)
{
  if (thisTab != syvum_selected_tab)
    {
      var bgChosen = "maroon";
      var fgChosen = "white";
      document.getElementById("syvum_" + syvum_selected_tab + "_tab_span").style.backgroundColor = fgChosen;
      document.getElementById("syvum_" + syvum_selected_tab + "_tab_span").style.color = bgChosen;
      document.getElementById("syvum_" + syvum_selected_tab + "_tab_span").style.cursor = "pointer";

      document.getElementById("syvum_" + thisTab + "_tab_span").style.backgroundColor = bgChosen;
      document.getElementById("syvum_" + thisTab + "_tab_span").style.color = fgChosen;
      document.getElementById("syvum_" + thisTab + "_tab_span").style.cursor = "";

      document.getElementById("syvum_" + thisTab + "_tab").style.display = "";
      document.getElementById("syvum_" + syvum_selected_tab + "_tab").style.display = "none";

      if (shown_tab_contents[thisTab] == 0)
        {
          makeRequest(tab_urls[thisTab]);
        }

      syvum_selected_tab = thisTab;
    }
}

function makeRequest(url)
{
  var http_request = false;
  if (window.XMLHttpRequest) // Mozilla, Safari,...
    { 
      http_request = new XMLHttpRequest();
    }
  else if (window.ActiveXObject) // IE
    {
      try {
            http_request = new ActiveXObject("Msxml2.XMLHTTP");
          }
      catch (e)
          {
            try
              {
                http_request = new ActiveXObject("Microsoft.XMLHTTP");
              }
            catch (e) {}
          }
    }

  if (!http_request)
    {
      window.location.href = tab_alternate_urls[syvum_selected_tab];
      return false;
    }
  http_request.onreadystatechange = function() { alertContents(http_request); };
  http_request.open('GET', url, true);
  http_request.send(null);
}

function alertContents(http_request)
{
  if (http_request.readyState == 4)
    {
      if (http_request.status == 200)
        {
          document.getElementById("syvum_" + syvum_selected_tab + "_content").innerHTML = http_request.responseText;
          shown_tab_contents[syvum_selected_tab] = 1;
        }
      else
        {
          window.location.href = tab_alternate_urls[syvum_selected_tab];
        }
    }
}