EXCERPT

Across the country, the goal of ensuring that qualified voters can cast their votes is achieved in vastly different ways � and sometimes not at all. Over half the states offer provisional voting, affidavit voting or fail-safe voting � different methods to ensure voters lost in the system are not denied the opportunity to cast a ballot. In many other states, voters can appeal to a judge if their name doesn�t appear on the list of registered voters. In several other states, voters not on the registration list have no recourse and are not permitted to vote.

Full text can be found online at:
http://www.electionline.org/site/docs/pdf/prov_voting.pdf