Software⏱️ 3 min read📅 2026-06-19

How to Fix: Getting different 404 Error Extensions for the same file IIS8

IIS8 configuration issue causing different 404 error extensions for the same file.

Quick Answer: Check IIS8 configuration and ensure that the correct MIME type is set for the file. You can do this by editing the web.config file or using the IIS Manager to configure the MIME types.

📋 Table of Contents

  1. ⚠️ Common Causes
  2. 🛠️ Step-by-Step Verified Fixes
  3. 🎯 Final Words

We have a web application hosted in IIS 8 on a Windows 8 Beta Server. When browsing a file from IIS, we're getting different 404 error extensions for the same file every time. This issue is frustrating because it indicates that the file exists but can't be accessed correctly.

The presence of different error extensions for the same file raises questions about the configuration and settings of our IIS server.

⚠️ Common Causes

  • The primary reason for this issue lies in the way IIS handles file extensions and MIME types. By default, IIS uses a mapping table to determine the file extension and its corresponding handler. However, if this mapping is not properly configured or is incomplete, it can lead to incorrect handling of files.
  • Another possible cause could be related to the order of handlers in the configuration file (web.config). If the correct handler for a particular file extension is not specified at the top of the list, IIS might default to an incorrect handler, resulting in 404 errors.

🛠️ Step-by-Step Verified Fixes

Configuring the MIME Type Mapping Table

  1. Step 1: Open the IIS Manager and navigate to the 'MIME Types' section under the 'Application Pool' settings. Then, click on the '+' button to add a new mapping.
  2. Step 2: In the 'Add a New MIME Type' dialog box, enter the file extension (e.g., '.aspx') in the 'File Extension' field and select the corresponding handler (e.g., '.aspx' -> 'ASP.NET Web Page Handler').
  3. Step 3: Repeat this process for all relevant file extensions to ensure that their correct handlers are mapped.

Verifying Handler Order in web.config

  1. Step 1: Open the web.config file associated with your application and verify that the handler for each file extension is specified at the top of the 'handlers' section.
  2. Step 2: If necessary, reorder the handlers to ensure that the correct one comes first. For example, if you have a handler for '.aspx' files but it's not listed at the top, move it there to take precedence over other handlers.

🎯 Final Words

After configuring the MIME type mapping table and verifying the handler order in web.config, restart IIS services and test your application again. If issues persist, consider further investigation into IIS configuration or server-side issues.

Did this fix your problem?

If not, try searching for specific error codes.

🔍 Search Error Database

❓ Frequently Asked Questions

🛠️ Related Fixes

How to Fix: Pc crashes shortly after launching game (rainbow

Fix Pc crashes shortly after launching game (rainbow six siege). Compl

How to Fix: Installing an APK on a locked down phone

Installing an APK on a locked down phone: Try using a rooted device, e

How to Fix: New PC build- no signal and no clue

Fix New PC build- no signal and no clue. Complete troubleshooting guid