HTTP Error 500.24 - Internal Server Error An Asp.NET setting has been detected that does not apply in Integrated managed pipeline mode

Question

I have webpage which has gridview, one of the columns will have a image. When clicked on image it will open the PDF saved on the web server. It was working fine but I am getting

Answer 1

One may get this error when accessing a wrong path (e.g., on the url parameter of an Ajax call), even though all of the other answers suggestions were handled.

For the correct usage of (relative) paths, see this answer.