In IIS 7, you can control the detailed error messages being sent to the clients. By default, the detailed error messages can be viewed only by browsing the site from the server itself.

But, this is dangerous because Detailed errors may contain about the inner workings of your web-site. We should allow only trusted persons to see the detailed error messages, that's why it is configured default to be viewable only from the server.

Example : For a 404.0 error, if the detailed error message is not enabled for the website, then the users will see the following on their browsers:

Server Error

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HTTP Error 404 - File or directory not found.

If the web browser is installed on the same physical machine as IIS is installed on, the error message may resemble the following:

Server Error in Application "<application name>"

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HTTP Error 404.0 - Not Found

This will be followed by HRESULT, possible cause and resolutions sections.

If you want to enable this detailed error message to be shown on the clients as well, then you need to change the setting in the IIS7 manager.

Follow the below steps for the same:

1. Open the IIS7 manager

2. Select the Website and on its features view, double click on “Error Pages”.

3. Right click and select the “Edit Feature Settings…” or select the same from the Actions pane (in the right hand side)

4. Select the “Detailed errors” radio button and click on OK

5. Now, even your client browsers will be able to see the detailed error messages.

This article gives more information on this detailed error messages with IIS7.

Hope this helps!