Whiteboards are designed to be used with dry erase markers, which wipe off easily with the use of an eraser, cloth or paper towel. Unfortunately, it can be very easy to pick up a permanent marker and use it on a whiteboard if you aren't paying attention. Even though the dyes in permanent-marker ink are meant to be non-washable, you can remove this ink from smooth surfaces such as white boards using a very simple technique.
Draw over the stained area with a dry erase marker of any shade. Cover the permanent marker ink thoroughly with the ink from the dry erase marker.
Erase the entire area with a dry erase eraser, soft cloth or paper towel.
Squirt some dry erase board cleaner onto the board, and wipe it off with a paper towel to remove any lingering residue.