The first three sites here will be able to give you the information you need.
http://www.google.com/search?hl=en&source=hp&ie=ISO-8859-1&q=War+Powers+Act+&btnG=Google+Search
Does the War Powers Act serve to constrain or expand the President's ability to take the nation to war?
2 answers
Why did politics fall out of favor? Is it now back in favor?