Actually most European countries are 230V not 240V (though that was the standard in some countries previously (like the UK who dropped it for easier compatibility with continental systems (back in 93))).

Prior to harmonisation Europe was mostly 220V so 230v was the average of the two common systems (in reality because of tolerances there are big overlaps).

http://www.nottingham.ac.uk/etc/guide-voltageoptimisation.ph...

Interestingly while the standard is 230v the average supply in the UK is 242V (but within the tolerance of the standard).