Help! Need X,Y coordinates of a grid table

I've got a very large grid of squares (each square is 10x10 pixels), and I need to be able to get the coordinates of those squares (as opposed to coordinates of each pixel) simply by clicking on them.

Clicking on them could allow for a tooltip or pop-up, but it would even better if the information could be added to a submission form.

Any ideas would be much appreciated. I am very new to JavaScript. It seems like a rather easy language, but this is my first attempt at learning a language (other than HTML), and when I say newbie, I'm referring to yesterday!

Thanks to all in advance!