Bleach will whiten and disinfect diapers, but it will also cause them to wear out faster. Chlorine bleach eats your diapers away!  Alternative means of whitening/disinfecting include using borax, or  occasionally using chlorine-free bleach such as oxygen bleach or hydrogen peroxide bleach.  Minor stains will not harm baby and will usually wash out eventually, but if you wish to hasten stain removal, just hang the diaper in the sun (the UV rays will also sanitize the diaper).