The requested page cannot be accessed because the related configuration data for the page is invalid.

As part of my work recently I was moving SQL Monitor from the bespoke XSP web server to be hosted on IIS instead. This didn't go smoothly. I was lucky to be helped by Red Gate's support team (http://twitter.com/kickasssupport).

I had SQL Monitor installed and working fine on the XSP site but wanted to move to IIS so I reinstalled the software and chose the IIS option. This wasn't possible as IIS wasn't installed on the server. I went to Control Panel, Windows features and installed IIS and then returned to the SQL Monitor installer. Everything went as planned but when I browsed the site I got a huge error with the message

"HTTP Error 500.19 - Internal Server Error
The requested page cannot be accessed because the related configuration data for the page is invalid."

All links that I could find suggested it was a permissions issue, based on the directory where the config file was stored. I changed this any number of times and also tried the altering its location. Nothing resolved the error. It was only when I was trying the installation again that I read through the details from Red Gate and noted that they referred to ASP settings that I didn't have. Essentially I was seeing this. I had installed IIS using the default settings and that DOESN'T include ASP.

When this dawned on me I went back through the windows components installation process and ticked the ASP service within the IIS role. Completing this and going back to the IIS management console I saw something like this; so many more options! When I clicked on the Authentication icon this time I got the option to not only enable Anonymous Authentication but also ASP.NET Impersonation (which is disabled by default).

Once I had enabled this the SQL Monitor website worked without error.

I think the HTTP Error 500.19 is misleading in this case and at the very least should be able to recognise if the ASP service is installed or not and then to include a hint that it should be.

I hope this helps some people and avoids wasting as much of your time as it did mine. Let me know if it helps you.