Troubleshooting 'IIS 404 Not Found' Errors

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When attempting to access a webpage via Internet Information Services (IIS) version 8 and encountering an HTTP 404 error, followed by the message 'The webpage cannot be found,' there are several potential causes that may need investigation.

Common Causes of IIS 404.0 Error

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1. Missing or Non-Existent File

Ensure that the requested file actually exists within its designated directory on your server's hard drive. Also, double-check for any typos in both the URL path and file name since a single character discrepancy can lead to this error.

2. Incorrect Filter/Module Configuration

Verify whether the correct filter or module is being used for serving static files (such as images, CSS, JavaScript) within IIS's configuration settings. Sometimes, after an update, IIS might not automatically reconfigure these settings correctly.

3. Disabled Directory Browsing

Ensure that directory browsing has not been intentionally disabled at either the website level or root-level IIS configurations for the respective folder containing the requested file(s). To enable it:

1. Open Internet Information Services (IIS) Manager.

2. Double-click on 'Sites' in left-hand tree view if you're working with a specific site, otherwise click on 'Default Web Site'.

3. In right-hand panel under 'Home Directory' section find the appropriate path for which directory listing should be enabled.

4. Click on ‘Browse’ button next only once; then select “Read/Write” permissions from dropdown list below.

Troubleshooting Steps

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### Step 1: Enable Failed Request Tracing

Enable failed request tracing to gather more detailed information about the requests that are failing and why:

1. Open Internet Information Services (IIS) Manager.

2. Double-click on 'Failed Requests' in left-hand tree view under your desired site or application.

### Step 4: Review Trace Log Files

Once enabled, you can find trace log files within C:\inetpub\logs\W3SVC\'site_ID'/OLDDIR folder where 'site_ID' is replaced with actual GUID identifier for the affected website. These logs will contain valuable information about each request made to your site including HTTP status codes returned by server during processing.

### Step 5: Check IIS Configuration

In addition, ensure that none of these settings are preventing IIS from serving static files:

1. Open Internet Information Services (IIs) Manager.

2. Double-click on 'Static File' under 'Handler Mappings' section in left-hand tree view for your desired site or application.

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When facing an HTTP 404 error after updating to a newer version of IIS, follow these troubleshooting steps:

1. Ensure that the requested file exists and is correctly named.

2. Verify whether directory browsing has not been disabled at either website or root-level configurations.

3. Enable failed request tracing for additional logging information.

By following these simple yet effective solutions, you should be able to resolve 'IIS 404 Not Found' errors and ensure smooth operation of your web application(s) served via IIS version 8.

Iis 404 not found