There is a deadline which is at the end of the month (I reserve the right to extend this another month). After the puzzle is declared over, I will reveal the solution and choose my favourite of the answers sent in (any correct solution will get a prize).
This one will probably need you to visit at least one other website and will require some special skills. If you know how the answer works, but are incapable of finishing it, please send me your workings and if you've got far enough you'll get a prize.
The First, Second, Third and Fourth puzzles are still online. Their solutions are still not public knowledge, and the fourth has never been solved.
The first puzzle was solved by Longbird and later by Mr Stewart. The second has still only been solved by Longbird. The third was solved by Longbird and Kevan.