After the silly mistake I made working out the energy needed to heat some water (it was late and I had just finished work), I got to thinking about how hard would it be to add a few calculators onto this site. I had a quick look around and there seems to me dozens of example about using javascript to process 'stuff'.  But to be honest, it is all Greek to me. So two birds could be killed with one stone.  Calculators to work out frequently asked questions and an easy to follow tutorial a