eyecager:

SOURCE-  http://draugdesign.com/2011/stepbackwardsmart

“Every now and then Photoshop switches your active layer when you use the undo or stepback command. This cause me sometime to painting in the wrong layer. I found this so frustrating that I scanned the entire Internet for a solution. Late april i found this script. Place the .jsx file in photoshop/presents/scripts. 
Then assign ‘command+z’ (ctrl+z) as the a hotkey. I altso removed the step backward hotkey.

THANK YOU Sinistergfx, who ever you are. THANK YOU THANK YOU. This PhotoShop Script have saved me so many gray hairs.

download : 
http://dl.dropbox.com/u/3580711/StepBackwardSmart.jsx “