The principle of ¨dont say or do anything online that you wouldnt do face to face" is basically saying you shouldnt say something to someone online just because youre hidden behind you screen, it could still be offensive and really damage someone´s self esteem and confidence. Another reason is that colleges can look back through your social media account and things that you have said online which helps determine their decision on whether or not they choose to accept you. In conclusion you should definitely think before you put something on the internet for all to see.