http://labeling.bayerhealthcare.com/html/products/pi/fhc/YAZ_PI.pdf-DOSAGE AND ADMINISTRATION-----------------------
Take one tablet daily by mouth at the same time every day. (2.1)
Tablets must be taken in the order directed on the blister pack. (2.1)
---------------------DOSAGE FORMS AND STRENGTHS----------------------
Yaz consists of 28 film-coated, biconvex tablets in the following order (3):
24 light pink tablets, each containing 3 mg drospirenone (DRSP) and
0.02 mg ethinyl estradiol (EE) as betadex clathrate
4 white inert tablets
If you look here, the four white pills have nothing in. They are blanks. This means you
do effectively get a break, so therefore everyone who takes it takes it 'back to back' (as in takes every pill in the pack, then goes on to the next pack). That's different to the 21 day pill packs where you are meant to take nothing for 7 days, but some people dont have the break and this is referred to as 'back to back'.
Hope that makes sense!