According to babel fish - it means squat!! Oh I need to find myself a young French lad who'll lead me astray.. hold on.. that happened last Summer.. lucky old me!!
Prolo in French is, I believe, equivalent to prole in English and that is an abbreviation of proletarian which means belonging to the poorest class. At a guess, therefore, I'd say "ça fait prolo" means something such as, "That makes you look like a bit of a chav!"