I've never been trained on these things, so I don't know how to do simple things, and I'm not sure what the terminology is. I'll do my best.
THE SITUATION
We have a new webserver, hosting our SharePoint website. (www.example.com)
I have a ASPX/C# files sitting on the same server.
A coworker has mapped a subdomain to the SharePoint server. (subdomain.example.com)
THE GOAL
I need to configure IIS such that whenever someone visits subdomain.example.com, they are presented with the ASPX/C# webpages.
MY ATTEMPTS
I Googled the issue, and found recommendations to create a site binding.
I did so, but this didn't resolve the issue.
Someone also mentioned host headers, but I didn't see anything on IIS named anything like that.
WHERE WE ARE
If I visit subdomain.example.com, I'm asked for login credentials.
If I put in administrator credentials for the server, I'm sent to a 404 page.
If I put in any other credentials, it rejects me, asking again for credentials.