What is required for an IIS site to send error details to the browser?

Question

I am receiving a Server Error on an ASP Classic site running on IIS 7.5.

I have "Send Errors To Browser" set to True, however I still receive the following error screen:

Answer 1

IIS is hijacking your classic ASP app's response. In your web.config file ensure that the following is configured:

<configuration>
    <system.webServer>
        <httpErrors existingResponse="PassThrough"/>
    </system.webServer>
</configuration>

Also make sure that you've enabled "Send Errors To Browser" in the ASP configuration feature for your site in IIS manager: