since most recent mobile phones charge through a micro usb except the iphone, i'm just curious if it's really ok to charge a let's say a SE phone to a nokia charger and vice versa? both my n900 and xperia pro are fine and gets charged but i'm just curious when i noticed the volts listed on the adapter are a bit different...

nokia charger

input 100-240~/ 50-60Hz/ 160mA/ 16VA
output 5 0V=/ 1200mA

sony ericsson charger

input 100-240VAC~150mA 50-60Hz
output 5.0 VDC = 850mA

No.

(10 chars)

If that were actually the case then it would indeed matter because you'd likely fry the phone with the lower input voltage when charging it with the charger of the other one.

But as the data you provided shows both of your chargers have the same output voltage of 5V. Since they are designed to be USB 2.0 compatible that's required.
What differs is the maximum electric current ("amperage"). USB 2.0 specifies it to be at least 500mA. In contrast to the voltage a higher maximum electric current doesn't do any harm. So it won't break anything if you charge your Nokia phone with the Sony charger and vice versa. The worst thing that might happen is that the Nokia won't charge with the Sony charger because it requires the higher electric charge of the Nokia charger. But most likely it will simply take a bit longer (about 1.5 times).

my n900 likes the charger of my HP touchpad best... charged in no time!