crwdns2934241:0crwdne2934241:0 mayer

crwdns2934249:0crwdne2934249:0:

If you are talking about the white ones, They are called LSI (liquid submersion indicators).  If the are exposed to moisture they turn red.  Apple will then use this to refuse warranty support.

crwdns2915684:0crwdne2915684:0:

open