When you add in an INCLUDE FILE to an ASP Document, with the same name of the file it is included in.

Using Includes helps keep your code organized. Sometimes, when we are in a hurry, we write the name of the file we're in instead of the file we need to include.
And this simple mistake will create the following error.

Name the file Main.asp
Now, add the include to it.
<!--#include file="main.asp">

This will cause the error.

The name of the file is Main.asp.
Create another file and add the information that needs to be included in the Main.asp file. Once the file has been created, insert the following statement to your Main.asp file.
<!--#include file="Other.asp">