# The Requested URL Was Not Found (404) Error

## Environment

<table>
	<tbody>
		<tr>
			<td>Product</td>
			<td>Progress® Telerik® UI for ASP.NET AJAX</td>
		</tr>
	</tbody>
</table>

## 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:

  ![](https://www.telerik.com/products/aspnet-ajax/documentation/assets/0412340b785b58f2fd71b8195a01f2d2/axd-presence-and-file-mapping.png)

* 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 3.5: web.config**

  ```
    <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 3.5-4.8: web.config**

  ```
    <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`](https://www.telerik.com/forums/404-not-found-error#RmyQAhZgg06uEBW4UOStRw)

* [`RadSpell Web.config 404 error`](https://www.telerik.com/forums/radspell-web-config-404-error#xquGbOZ4aUSY_07LCbuuew)

* [`RadAsyncUpload 404 loading Telerik.Web.UI.WebResource.axd`](https://stackoverflow.com/questions/23086554/telerik-radasyncupload-404-loading-telerik-web-ui-webresource-axd)

* [`RadEditor 404 File or directory not found`](https://www.telerik.com/forums/404-file-or-directory-not-found-when-i-click-image-manager-in-rareditor's)