I want to ask a phone number to the user and after that I want to get the missing information (Address...) from a web site to speed things up for the user.

For example I can go to the following web site and manually find those informations.

http://sympatico.msn.yellowpages.ca/index.html?gl=en_CA

How do I find missing information to what could be that same web site (or any other)?

How does this work?

Any information on that topic is appreciated.