<p>I have a standard HTML image tag with an image in it, 100 by 100 pixels in size. I want people to be able to click the image and for that to pass the X and Y that they click into a function.</p>

<p>The coordinates need to be relative to the image top and left.</p>

I think you're talking about:
```
```
<input id="info" type="image">
```
```
When submitted, there are form values for the x and y coordinate based on the input element id (
```
info.x
```
and
```
info.y
```
in this case).
http://www.w3.org/TR/REC-html40/interact/forms.html#h-17.4.1