var oXmlHttp = null;
  var iInterval = 1000;
  var iLastCommentId = -1;
  var divNotification = null;
  var blnRequestsEnabled = true;
  
  function checkComments() {
  
      if (blnRequestsEnabled) {
          try {
              if (!oXmlHttp) {
                  oXmlHttp = zXmlHttp.createRequest();
              } else if (oXmlHttp.readyState != 0) {
                  oXmlHttp.abort();
              }    
              
              oXmlHttp.open("get", <CheckComments.php>, true);
              oXmlHttp.onreadystatechange = function () {               
                  
                  if (oXmlHttp.readyState == 4) {
                      if (oXmlHttp.status == 200) {
          
                          var aData = oXmlHttp.responseText.split("||");
                          if (aData[0] != iLastCommentId) {                   
                              
                              if (iLastCommentId != -1) {                        
                                  showNotification(aData[1], aData[2]);
                              }
                              
                              iLastCommentId = aData[0];
                          }
                          
                          setTimeout(checkComments, iInterval);             
                      } else {
                          throw new Error("An error occurred while making the request.");
                      }                        
                  } 
              };    
          
              oXmlHttp.send(null); 
          } catch (oException) {
              blnRequestsEnabled = false;
          }
      } //End: if     
  }
  
  function showNotification(sName, sMessage) {
      if (!divNotification) {
          divNotification = document.createElement("div");
          divNotification.className = "notification";
          document.body.appendChild(divNotification);
      }
      
      divNotification.innerHTML = "<strong>New Comment</strong><br />" + sName 
                + " says: " + sMessage + "...<br /><a href=\"ViewComment.php?id=" 
                + iLastCommentId + "\">View</a>";
      divNotification.style.top = document.body.scrollTop + "px";
      divNotification.style.left = document.body.scrollLeft + "px";
      divNotification.style.display = "block";
      setTimeout(function () {
          divNotification.style.display = "none";
      }, 5000);
  }
  
  //if Ajax is enabled, assign event handlers and begin fetching
  window.onload = function () {
      if (zXmlHttp.isSupported()) {
          checkComments();              
      }
  };