how to set photoshop to default on a mac because i been working on a image and i saved it then i opened it and now blocks of my pic are missing what cause it bc this is the second time it has happened and resetting the tool fix it please help me in any way u can
Resetting the preferences isn't going to help this.
Missing blocks in the image can caused by a few things: bad disks, corruption of the file by other software (a couple of font managers did this), bad RAM, and bad video cards, and every once in a great while an actual bug in Photoshop (but we fix those as soon as we find them).
Does the image change as you zoom in and out? If so, it's RAM or the video card.
Do you use any font manager plugins? If so, try disabling them.