Classic ASP is the good old Active Sever Pages technology which was the way Microsoft rendered web sites before the advent of managed code and ASP.NET.
It is essentially just a directory of asp, htm and other static content.
It's not supported by Microsoft e.g. there is no Classic ASP project type in VS 2010. May might just as well use Notepad (as I've seen some people do!).
Anyway, needed to do some work with this using the Classic .NET AppPool and got:
"The page you are requesting cannot be served because of the extension configuration. if the page is a script, add a handler. if the file should be downloaded, add a mime map."
Mr Google suggested IIS Handler Mappings but when I looked there I saw that ISAPI.dll was disabled (no way to enable it) and the message:
"You must manage managed handlers directly in the configuration file"
Come in Mr Google - your time is up.
Eventually found the solution under Windows Features:
Under IIS / World Wide Web Services / Application Development Features:
ASP = On
ISAPI Extensions = On
ISAPI Filters = On
Under IIS / World Wide Web Services / Common HTTP Features:
Static Content = On