Fuzz testing or fuzzing is a software testing technique that provides random data ("fuzz") to the inputs of a program. If the program fails (for example, by crashing, or by failing built-in code assertions), the defects can be noted.

The great advantage of fuzz testing is that the test design is extremely simple, and free of preconceptions about system behavior. Fuzz testing was developed at the University of Wisconsin-Madison in 1988/89 by Professor Barton Miller and the students in his graduate Advanced Operating Systems class.

Powerfuzzer is a highly automated web fuzzer based on many other Open Source fuzzers available (incl. cfuzzer, fuzzled, fuzzer.pl, jbrofuzz, webscarab, wapiti, Socket Fuzzer) and information gathered from numerous security resources and websites. It is capable of spidering website and identifying inputs.
http://powerfuzzer.sourceforge.net/