This is a link to the Philips Dead Pixel Policy
http://www.p4c.philips.com/files/1/170s5fs_05/170s5fs_05_ppd_eng.pdf
different monitors have different criteria for what is acceptable and what isn't; meaning it depends on the model of your monitor as to what their policy towards it is.
some models do have a zero pixel policy but only certain models, which is probably why you cannot find information about it.
worth looking at the dead pixle policy before buying a monitor.
My monitor (170s5fs) has 2 adjacent always on sub-pixels which apparently is acceptable (only just). But their warranty states that they will deliver a new monitor within 48 hours and take the old one away, so im going to lie and say i have 3 adjacent sub-pixles (which means 1 white pixle) so they deliver a new one and take my old one.
By the time they check it and see that i made a mistake, they'll have delivered my new one.