Is the difference between "look good" and "look well" the same as "feel good" vs "feel well"?
Are you feeling all right? You don't look so [good/well].
If you say "You look really good!", you are more likely to be commenting on their overall appearance - clothes, hair, makeup (if appropriate) etc.
Remember - if you don't use correct capitalisation, punctuation and spacing, anything you write will be incorrect.