Choose the number of strings, your
tuning, root note and scale and click Go! Simple eh!
By selecting a position, you'll get the different scale positions
highlighted.
The fret markers option will draw a line at the 3rd, 5th, 7th, 9th 12th frets and so on (where dot markers would be on a regular guitar)
Uncheck the replace current scale option to add several scales to one page.
If you want to print these out, you'll need to tell your browser to print background colours to see the highlighted boxes on the fretboards. There'll be an option in print settings somewhere. In IE8 and firefox, just go to page setup. For other browsers you may have to dig around in the settings.