The answer to your question would be that the verbs that correctly complete the sentence are <em>has been mapped</em> and <em>are missing.</em>
Explanation:
In any sentence, there should be subject verb agreement. It means that the subject and the predicate must agree in number, that is, both need to be singular or both need to be plural. In the first part of the sentence, the subject is singular <em>most of the site, </em>so the verb should also be singular (has been mapped). Then, in the second part of the sentence, the subject is plural. Consequently, the verb should be plural (are missing).
It's better because you get to actually see your friends and be able to fun instead of learning on the computer and seeing your friends through the screen.