StackOverFlow WCF&JSON Example not working, no endpoint

StackOverFlow WCF&JSON Example not working, no endpoint

guys. My question arises from an older post: Send JSON to WCF 3.5 using Ajax
On that page, the second answer was accepted with some modifications. I
created a project using VS2012 under windows 7 PC, and basically did
copy-and-paste. However, I found it not working properly. As I opened it
in IE, it gave a message of "no endpoint found" I did some search and
didn't find where the problem could be.
Class name and file structure are same as the code posted on the page I
referred to. Could you guys give some hints of what it could be? Thanks in
advance.