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ASP.NET 404 ERROR PAGE - How to Configure Error 404 Page in ASPX (.NET) for IIS Server?

ASP.NET 404 ERROR PAGE - How to Configure Error 404 Page in ASPX (.NET) for IIS Server?

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How to Configure Error 404 Page in ASPX (.NET) for IIS Server

When someone visits a page on your website that does not exist, they see a 404 Error or "Page Not Found" message. Instead of showing a plain error, you can display a custom 404 page that helps visitors find their way back to your website.

If your website is built using ASPX (.NET) and hosted on Microsoft IIS (Internet Information Services), configuring a custom 404 page is simple.

In this guide, you'll learn how to configure a custom Error 404 page step by step.

What is a 404 Error Page?

A 404 Error appears when a visitor requests a webpage that cannot be found on the server. This may happen because:

  • The page was deleted.
  • The URL was typed incorrectly.
  • The page was moved to another location.
  • A broken link points to a page that no longer exists.

A custom 404 page provides a better user experience by helping visitors continue browsing your website.

Before You Start

Make sure you have:

  • An ASPX (.NET) website.
  • Access to your IIS Server.
  • Permission to modify your website settings.

Step 1: Create a Custom 404.aspx Page

Create a Custom 404.aspx Page

Create a new page in your ASP.NET project named:

404.aspx

Add a simple message such as:

<h1>Oops! Page Not Found</h1>

 <p>Sorry, the page you are looking for doesn't exist.</p>

<a href="Default.aspx">Go Back to Home</a>

You can also add:

  • Your company logo
  • Search box
  • Navigation menu
  • Contact information

This makes the error page more useful for visitors.

Step 2: Publish the Website

Publish a Custom 404.aspx Page

Save your project and publish it to your IIS server.

Make sure the new 404.aspx file is available in your website folder on the server.

Step 3: Open IIS Manager

404.aspx Page : Open IIS Manager
  1. Press Windows + R.
  2. Type:

inetmgr

  1. Press Enter.

This opens the Internet Information Services (IIS) Manager.

Step 4: Select Your Website

404.aspx Page : Select Your Website

In the left panel:

  • Expand your server name.
  • Expand Sites.
  • Click your website.

The website settings will appear in the middle panel.

Step 5: Open Error Pages

404.aspx Page : Open Error Pages

In the Features View:

  • Double-click Error Pages.

This section controls how IIS handles different error messages.

Step 6: Configure the 404 Error Page

404.aspx Page : Configure the 404 Error Page
  1. Locate 404 in the list of HTTP status codes.
  2. Right-click 404.
  3. Choose Edit Feature Settings or Edit (depending on your IIS version).
  4. Select Execute a URL.
  5. Enter:

/404.aspx

  1. Click OK.

This tells IIS to display your custom ASPX page whenever a visitor reaches a missing page.

Step 7: Configure web.config (Recommended)

404.aspx Page : Configure web.config

Open your website's web.config file and add the following configuration:

<system.web>

    <customErrors mode="On" defaultRedirect="404.aspx">

        <error statusCode="404" redirect="404.aspx"/>

    </customErrors>

</system.web>

If your application uses IIS 7 or later, you can also configure:

<system.webServer>

    <httpErrors errorMode="Custom">

        <remove statusCode="404"/>

        <error statusCode="404"

               path="/404.aspx"

               responseMode="ExecuteURL"/>

    </httpErrors>

</system.webServer>

These settings ensure both ASP.NET and IIS display your custom error page correctly.

Step 8: Test Your 404 Page

404.aspx Page : Test Your 404 Page

Open your website in a browser.

Now enter a URL that does not exist, for example:

https://www.yourwebsite.com/unknownpage.aspx

If everything is configured correctly, your custom 404.aspx page will appear instead of the default IIS error page.

ASP.NET 404 Error Page

Tips for a Good 404 Page

A useful 404 page should:

  • Clearly explain that the page cannot be found.
  • Include a link to the homepage.
  • Display your website logo.
  • Provide navigation to important pages.
  • Include a search option if available.
  • Match the design of your website.

A helpful 404 page can keep visitors on your website instead of making them leave.

Common Problems

The default IIS error page still appears.

Check that:

  • The 404.aspx file exists.
  • The path is correct.
  • IIS has been restarted if required.
  • The web.config file is saved correctly.

The page opens but shows another error.

Verify that:

  • The ASP.NET application is running.
  • The page has no coding errors.
  • File permissions are correct.

Conclusion

A custom Error 404 page is a small improvement that creates a much better experience for your visitors. Instead of seeing a confusing system message, users receive helpful guidance that keeps them engaged with your website.

By creating a 404.aspx page, configuring IIS, updating the web.config file, and testing your setup, you can ensure that missing pages are handled professionally.

Even if you're new to ASP.NET and IIS, these steps make it easy to create a polished and user-friendly 404 error page.

Frequently Asked Questions (FAQs)

1. What is a 404 Error?

A 404 Error means the requested webpage cannot be found on the server.

2. Why should I create a custom 404 page?

A custom 404 page helps visitors find useful links instead of leaving your website after seeing an error.

3. Where should I place the 404.aspx file?

Place it in the root folder of your ASP.NET website unless your application structure requires a different location.

4. Do I need to edit the web.config file?

Yes. Configuring customErrors and httpErrors helps ensure the custom page works correctly for both ASP.NET and IIS.

5. How do I test my custom 404 page?

Open your website and visit a URL that doesn't exist. If configured correctly, your custom 404.aspx page will be displayed.