my friends tell me..."lift until you cant lift anymore" (which is about 8 or 10 reps with the heavy weights)...say if i were doing biceps....then i would go until i couldnt curl anymore....then rinse repeat....

i was told that u gain muscle size when u lift heavier weights for less reps and u gain strength when u do more reps with less weights

i am only interested in gaining muscle size for now

here is my workout:

bench press (until failure, 8-10 reps)
biceps (15 reps each arm until failure)
shoulders (30's if anyone knows what that is, and shrugs)
triceps (10 reps of skullcrushers until failure)
abs (50 reps)
then i repeat 4 more times

am i doing anything wrong?
am i missing a muscle?

thanks a lot much help needed