Send Mail to Admin same the Registered User

I search the same topic in our DNS.. But I'm not clear with that.. One..

In my web application, I'm developing the registration page.

When the user fill the registration form and click the Register button that

time the E-mail send to both the Register User/Person and the Site Admin...

How to do this?...

If possible I need the coding...

Thanks in Advance

Regards,