Today I was working on a Node server that runs on a Windows server with IIS. I ran into a problem where I wanted my 404 errors to actually send a 404 result with a custom page created in Node. Sending a 404 error made IIS want to display its custom 404 error page though.
I learned you can get around this by adjusting your web.config file. Locate your
<system.webServer> settings and add the following snippet:
<httpErrors existingResponse="PassThrough" />. This leaves the response untouched if an existing response exists per.
Side note, I highly recommend using the IIS Node package if you are one of the rare people who have to run this setup.