Wooden shed, needs ventilation - drilling holes ok?

I have a wooden shed which I think is around 8 feet by 4 feet. It was built around 1998 (before I moved into house).

There appears to be no ventilation built into the design of the shed and this concerns me.

Is it ok to simply drill a few holes at the front and back of the shed? If so should they go near the top or bottom, how many and how big should they be?

my shed is fairly air tight most arnt i have no ventilation
you only need to increase ventilation if you have damp as wood breaths
usually if you have damp or condensation you need to cure the problem first

http://s21.photobucket.com/user/bigall2005/library/?sort=3&page=1
http://s21.photobucket.com/user/bigall2005/slideshow/
it is now fully insulated and lined with 12mm ply