Resetting an objects center of rotation

Hello, Often when i modelling an objects center of rotation (well thats what i am calling it here as i dont know the proper name) appears way outside the object this is irratating if i am trying to rotate it or scale it

http://img223.imageshack.us/img223/8427/annoyingbn0.png

Thats an example the white dot is the problem i think

Is there anyway to make that white dot appear inside the object?

Thankyou in advance

http://skypa.mine.nu/blender.center.new.png

Brillant Thankyou so much =D