THe workaround listed below works, but does require the user to zoomin/out or interact with the map in some manner after unchecking the box, so its not really a valid workaround. Another workaround would be to disable the checkbox next to the graphics datatable. The workaround is to turn off the alert window by commenting out the code in JavaScript. And then put code in Toc1_NodeChecked event. Please follow the steps.1. Set UseDefaultWebResources property of all ADF web controls as false.2. Open display_dotnetadf.js in the folder <a href="file:C:/Inetpub/wwwroot/aspnet_client/ESRI/WebADF/JavaScript" target="_blank">C:\Inetpub\wwwroot\aspnet_client\ESRI\WebADF\JavaScript</a>3. Comment out this line of code:alert("An unhandled exception has occurred:" + argument);4. Put the server side code into Toc1_NodeChecked event, such as: protected void Toc1_NodeChecked(object sender, ESRI.ArcGIS.ADF.Web.UI.WebControls.TreeViewPlusNodeEventArgs args) { if (Toc1.Nodes[0].Nodes[0].Checked) { //to do } else { } }