If you’re using a GPS and coming via Fort William on the A82, you’re likely to be directed to turn left onto the A830 which takes you to the ferry from Mallaig on the mainland to Armadale on the Isle of Skye. This is fine if you want to use the ferry, but do check the timetables, http://www.calmac.co.uk/timetables. If you ignore the GPS and continue on the A82 then the A87 you will arrive at the Skye Bridge which is free.