javascript event clientX, clientY

Indicate the horizontal (x) and vertical (y) coordinate of the mouse at the moment the current event fired. These coordinates are relative to the viewable document area of the browser window or frame. To convert these coordinates to the document's in IE, be sure to add the body element's scroll values (or html element's scroll values in IE 6 standards-compatible mode). For Netscape 6, the pageX and pageY properties provide coordinates in the document's space.