Cannot find the X.509 certificate

Recently while working on the WCF services i came across the error "Cannot find the X.509 certificate". I searched a bit but none of the answers were matching my scenario. Here is my application details.

1. Service is WCF service Library
2. Services are hosted in IIS 6.0
3. Client is ASP.Net calling these services.

I have installed the cerficates and changed the configurations in app.config file. The most important thing is when you are hosting it IIS you also need to change the Web.config File accordingly. Please replicate the same to web.config file.

Though of putting it here so that someone should not waste 1 or 2 hour finding why is it not working as I did :)