Arrange the tiles so that they're in ascending order, with the empty space in the bottom right corner. The top row should read 1,2,3,4, the second 5,6,7,8 and so on. Refresh the page to get a new grid. Good luck.
Feedback, particularly code improvements, welcome. Send it to jonrob DOT one AT googlemail DOT com.
Original inspiration for creating this game came from Simon Tatham's Portable Puzzle Collection. I hope to recreate more of these in JavaScript + HTML5 canvas as I learn to program.
Code for detecting and correctly placing mouse clicks came from Dive Into HTML5 - an excellent book.