GenericErrorPage.htm missing

Question

What is this page for? I have an entry in the configuration file... do this cause any harm?

  <customErrors mode="off" defaultRedirect="GenericErrorPage.htm">
            <error statusCode="403" redirect="NoAccess.htm" />
            <error statusCode="404" redirect="FileNotFound.htm" />
        </customErrors>

Is the below error from GenericErrorPage.htm

Server Error in '/' Application.
--------------------------------------------------------------------------------

Runtime Error 
Description: An application error occurred on the server. The current custom error settings for this application prevent the details of the application error from being viewed remotely (for security reasons). It could, however, be viewed by browsers running on the local server machine. 

Details: To enable the details of this specific error message to be viewable on remote machines, please create a <customErrors> tag within a "web.config" configuration file located in the root directory of the current web application. This <customErrors> tag should then have its "mode" attribute set to "Off".


<!-- Web.Config Configuration File -->

<configuration>
    <system.web>
        <customErrors mode="Off"/>
    </system.web>
</configuration>


Notes: The current error page you are seeing can be replaced by a custom error page by modifying the "defaultRedirect" attribute of the application's <customErrors> configuration tag to point to a custom error page URL.


<!-- Web.Config Configuration File -->

<configuration>
    <system.web>
        <customErrors mode="RemoteOnly" defaultRedirect="mycustompage.htm"/>
    </system.web>
</configuration>

Answer 1

If an error occurs and the status code is different than 403 or 404 it will redirect to GenericErrorPage.htm

Also you have an error in your declaration. The mode attribute should be Off instead of off:

<customErrors mode="Off" defaultRedirect="GenericErrorPage.htm">
    <error statusCode="403" redirect="NoAccess.htm" />
    <error statusCode="404" redirect="FileNotFound.htm" />
</customErrors>

Answer 2

Basically if a user gets any error other than 403 or 404 (most notable other than those is 500 which is sent if there's an exception) they'll be redirected to that page, which won't exist (And if you're in IIS7 integrated pipeline or have IIS6 wildcard mapped they'll then get bounced to FileNotFound.htm - otherwise they'll just see a standard 404).

It'd probably be nice to at least give the user a "Oh no! Something is wrong!" page.

Answer 3

The files 'GenericErrorPage.htm', 'NoAccess.htm' and 'FileNotFound.htm' are default filenames, created by Visual Studio when creating a web application. You can use any HTML file or aspx page and use that name in the web.config. These names are just dummy values.