Whats the oficial sitefor green card?

Question

and i would alsow want to know if its free to register

Answer 1

The web site to find information about obtaining lawful permanent resident status (getting a "green card") is:

http://www.uscis.gov

There is no registration.  Your eligibility for lawful permanent resident status will correlate with the appropriate fee(s)

Answer 2

If you meant the site for the green card lottery, then it's http://www.dvlottery.state.gov -- and yes, registration is free.

Other than that, if you weren't looking specifically for the green card lottery, then refer to http://www.uscis.gov/greencard