Also known as the "Personal Responsibility and Work Opportunity Reconciliation Act of 1996."The bill was hammered out in a compromise with the Republican-controlled Congress, and many Democrats were critical of Clinton's decision to sign the bill. In fact, it emerged as one of the most controversial issues for Clinton within his own party.
One of the bill's provisions was a time limit. Under the law, no person could receive welfare payments for more than five years, consecutive or nonconsecutive.
Another controversial change was transferring welfare to a block grant system, i.e. one in which the federal government gives states "blocks" of money, which the states then distribute under their own legislation and criteria. Some states simply kept the federal rules, but others used the money for non-welfare programs, such as subsidized childcare (to allow parents to work) or subsidized public transportation (to allow people to travel to work without owning cars).
http://en.wikipedia.org/wiki/Welfare_reform