Display classic ASP errors

This is possible by adding the following to your web.config:

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

It will probably only be the following line:

<httpErrors errorMode="Detailed" existingResponse="PassThrought"/>

The rest, in fact, should already exist.