Now, I will explain how to configure custom error pages in IIS (Internet Information Service). For this example we will be using IIS 7.5 which shipped with Windows Server 2008 R2.

First Step, Open Internet Information Services (IIS) Manager.  Select your website. Note: This could also be set at the server level and applied to all sites on the server. DoubleClick on the “.NET Error Pages” icon.

The .NET Error Pages features view will be displayed.

Click the “Edit Feature Settings” link to enable this feature. The “Edit Error Page Settings” dialog box will appear.

How to determine the error code 404 explicitly..

First, On the .NET Error Pages Actions menu click the Add link.

The “Add Custom Error Page” dialog will appear. This is where we define individual error pages per status code. For our example we will add a custom page for the HTTP 404 Error.

Now that we have turned on the feature and added a custom page for the 404 status code we can verify it is working. Please reload your website.

As mentioned above this can also be managed from the site’s web.config file. Consider the following configuration section from our site’s web.config file.