Add .json file in asp.net web.config file

 How can I enable the download of *.json files from an old ASP.NET site (IIS6 I am led to believe)?

 I am getting a 404 page instead of the JSON file.

 Do I need to create a web.config file? What goes in it?

you can just add the following to your web.config in the system.webServer section:

<staticContent>
    <mimeMap fileExtension=".json" mimeType="application/json" />
</staticContent>