;D
It works.
_SFR_IO8(0x35) |= 4;
_SFR_IO8(0x35) |= (1<<4);
instead of _SFR_IO8(0x30) |= 4; according to the atmega168 documentation the MCUCR is located at 0x35.
i didnt check wich of both rules is the matching one, but at least one of both is working, cause my led is flashing in short terms an is i have a look into my serial console i receive the data of illumination.
if i take it into my hand and close is (100% dark) i get "0".
if there is minimal light i get "1". and so on. :o
max