James Handley's Javascript Su Doku Solver

Enter the numbers 1 to 9 as required into the grid, and press "solve" to try and solve it. Any input other than the digits 1 through 9 will be treated as that box being blank.

When you press solve, the computer will return as many boxes filled in as it can manage.
The boxes are coded as follows:

The checkbox makes the solver show the possibilities remaining for each unsolved square.