IIS 6.0 does not serve unknown MIME types

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Article ID: 326965 - View products that this article applies to.
This article was previously published under Q326965
IMPORTANT: This article contains information about editing the metabase. Before you edit the metabase, verify that you have a backup copy that you can restore if a problem occurs. For information about how to do this, see the "Configuration Backup/Restore" Help topic in Microsoft Management Console (MMC).
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SYMPTOMS

When you request a file from an IIS 6.0 Web server, and the file has a file name extension that is not a defined MIME type on the Web server, you receive the following error message:
HTTP Error 404 - File or directory not found.

CAUSE

Earlier versions of IIS include a wildcard character MIME mapping, which permits IIS to serve any file regardless of its extension. IIS 6.0 does not include this wildcard character MIME mapping and does not serve any type of extension that is not defined at the MimeMap node in the IIS metabase.

RESOLUTION

WARNING: If you edit the metabase incorrectly, you can cause serious problems that may require you to reinstall any product that uses the metabase. Microsoft cannot guarantee that problems that result if you incorrectly edit the metabase can be solved. Edit the metabase at your own risk.

NOTE: Always back up the metabase before you edit it.

To define a MIME type for a specific extension, follow these steps:
  1. Open the IIS Microsoft Management Console (MMC), right-click the local computer name, and then click Properties.
  2. Click MIME Types.
  3. Click New.
  4. In the Extension box, type the file name extension that you want (for example, .pdb).
  5. In the MIME Type box, type application/octet-stream.
  6. Apply the new settings. Note that you must restart the World Wide Web Publishing Service or wait for the worker process to recycle for the changes to take effect. In this example, IIS now serves files with the .pdb extension.
If you want to serve all files regardless of the file name extension (for example, if you cannot predict all files that will be served), follow these steps to add a wildcard character mapping:

Note You should only add the wildcard mapping to the IIS MIME map as a temporary solution during troubleshooting. After you have determined that a missing MIME type is the cause of the issue, remove the wildcard mapping and add the specific mapping for the MIME type that you need to serve.
  1. Open the IIS Microsoft Management Console (MMC), right-click the local computer name, and then click Properties.
  2. Click MIME Types.
  3. Click New.
  4. In the Extension box, type an asterisk (*).
  5. In the MIME Type box, type application/octet-stream.
  6. Apply the new settings. Note that you must restart the World Wide Web Publishing Service or wait for the worker process to recycle for the changes to take effect.
Note In addition to making these changes at the global level in IIS, you can add necessary MIME types at lower levels in the metabase. When you do this, you can specify the sites or directories that are permitted to serve content with a specific file name extension instead of globally allowing all sites to serve that extension.

STATUS

This behavior is by design.

MORE INFORMATION

More information about working with MIME types is available in the product documentation. To view this documentation, visit the following Microsoft Web site:
http://msdn2.microsoft.com/en-us/library/ms775148.aspx
You can also access the product documentation through the IIS Manager. For more information about how to access this Help feature, click the following article number to view the article in the Microsoft Knowledge Base:
815127 How to access IIS 6.0 Help documentation

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Article ID: 326965 - Last Review: December 3, 2007 - Revision: 6.6
APPLIES TO
  • Microsoft Internet Information Services 6.0
Keywords: 
kbpending kbprb KB326965

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