The Requested URL Was Not Found (404) Error

Updated on Oct 1, 2026

Environment

Product

Progress® Telerik® UI for ASP.NET AJAX

Description

When working with Telerik UI for ASP.NET AJAX, I get a 404 error that the requested URL was not found.

Solution

To solve the issue, use any of the following approaches:

• If the failing URL contains a session segment such as /(S(...))/default.aspx, check whether the application uses cookieless session state. URI-based session state inserts the session identifier into the request path, and routing, URL Rewrite rules, or IIS path handling can reject the resulting URL with a 404. As a diagnostic, switch the application to cookie-based session state and test the page again:

  XML

  <sessionState mode="InProc" cookieless="UseCookies" timeout="80" />

  If the page loads with UseCookies, the issue is related to the cookieless session URL rather than a Telerik .axd handler. Keep the required session mode and timeout for your application, and update the routing, rewrite, or IIS configuration if URI-based session state is required.

• In the IIS management console, check that the .axd extension (the default HTTP handler extension) is allowed under the Handler Mappings feature of IIS:

  

• Click the Edit button as displayed in the previous screenshot to check if the Verify if file exists checkbox is unchecked.

• If you are using Telerik® UI for ASP.NET AJAX, check if the ScriptResource.axd HTTP handler is correctly registered in your web.config as shown in the following statement:

  ASP.NET

    <add path="ScriptResource.axd" verb="GET,HEAD" type="System.Web.Handlers.ScriptResourceHandler, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" validate="false"/>

  .NET 3.5 and IIS7 Integrated Mode: web.config The following statement has to be present in the <handlers> section instead of <httpHandlers>:

    <handlers>
    	<add name="ScriptResource" preCondition="integratedMode" verb="GET,HEAD" path="ScriptResource.axd" type="System.Web.Handlers.ScriptResourceHandler, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" />   

  (For ASP.NET 4.0-4.8) Note that as of .NET 4.0 and later, the ScriptResource.axd instance is no longer needed in the web.config file. However, if you have it in your web.config, make sure that its Version value corresponds to the .NET version used by your Web Forms application.

• If you are using Telerik UI for ASP.NET AJAX and the ScriptManager, check if the Telerik.Web.UI.WebResource.axd HTTP handler is correctly registered in your web.config:

  ASP.NET

    <add path="Telerik.Web.UI.WebResource.axd" type="Telerik.Web.UI.WebResource" verb="*" validate="false" />

  IIS7 Integrated Mode: web.config The following statement has to be present in the <handlers> section instead of <httpHandlers>:

    <handlers>  
    	<add name="Telerik_Web_UI_WebResource_axd" path="Telerik.Web.UI.WebResource.axd" type="Telerik.Web.UI.WebResource" verb="*" preCondition="integratedMode" />

• Check if there is a firewall, proxy, or other similar networking configuration that does not allow access to the axd handler.

Note the following popular threads on the 404 error:

• 404 Not found error

• RadSpell Web.config 404 error

• RadAsyncUpload 404 loading Telerik.Web.UI.WebResource.axd

• RadEditor 404 File or directory not found