javascript - How to catch x and y position and reposition exactly in MVC4?

In a MVC4 app (targeting IE7+) I have an image. I want the user to be able to click on the image to position a little marker (image), and I want to store the relative x/y position related to the image so that I can reposition this pin when the user returns to this page again.

What is the best way to accomplish this?