"Let me fix that for you."
Used on internet forums when one takes it upon oneself to edit or correct somebody's words/images/material/whatever, usually with comical results.
Guy: Hey man, look at this cool Ed Hardy hat I bought!
Other guy: lmftfy... "Hey man, look at this douchebag hat I wasted my money on! I'm gonna wear it while I f*** my cousin!"
fuck + yeah + a lazy or food-filled mouth = f'gyeah
Mark: Jimmy, PIZZA!