Validates that the right system was built.

It is a kind of alpha testig,done by the developing 
organization.....when the product is not completed by the 
given time or "Time exceeds the deadline time".

User Acceptance testing is a Criteria in which we check 
that the product will match all the customer business 
requirement.

UAT is a testing done just after the system testing and 
before the release to check if all the customer's 
requirements are met and it is done from user(customer's) 
point of view.

User Acceptance testing is of two type those are:-
1)ALpha Testing:- to check project functionality and
application functionality at development area with clinet.
2)Beta Testing:- to check project functionality and
application functionality at client are with end user.

plz inform me if any thing worng..

user acceptence testing:
To ensure by testing build is ready to use or to delivery 
of types:
1)Alpha Testing: Testing conducted on the build with client 
at devlopment area
2)Beta Testing: Testing conducted on the build by end user 
at cutomers area