Just fill out the input table by clicking on the fields and choosing the desired numbers.
After you finished, just click on the "Solve" button, and let the magic happen. It shouldn't take more than a second.
In addition when it's done, a few awesome statistics will appear next to the solution.
Even if the given problem has multiple solutions you will only be able to see one of them, because in a problem like that the solution is not trivial, therefor the program has to take one or multiple guesses. Since the guesses are not random but calculated in order to maximize the chance of the correctness, the program will make the same guesses which will inevitably lead to the same answer every time.
In the case of a problem that has absolutely no solution, the given "solution" will be a table full of zeros.
(PS: If your browser is awesome you can use your keyboard to choose the numbers)