It seems the border is not taken into account in the JS offsetTop/Left properties, in FF 3.6. Excerpts

<div id="wall">
     <div id="small" class="zimg">
       <img src="..." 300x200/>
     </div>
     <br style="clear:both />
</div>

Some CSS

.zimg {
   border:20px solid #ddd;
    background:#eee;
   overflow:hidden;
    position:relative;
}

#wall {
  margin:50px 0 0 50px;
}


#small {
  width:300px;
  height:200px;
  float:left;
}

And a JS function to calculate the relative (x,y) coordinates of the mouse over the IMG

function objabs(o) 
{
   var x = 0,y = 0;

    console.log("get_abs: of "+o.id);
   while (o) {
        console.log("  "+o.id+" x("+o.offsetLeft+") y("+o.offsetTop+")  P:"+(o.offsetParent ? o.offsetParent.id : o.offsetParent));
      x += o.offsetLeft;
      y += o.offsetTop;
      o = o.offsetParent;
   }
   return [x,y];
}

Result: mouse (x,y) are always off by the size of the border (20px).
(console.log() is from Firebug to get a proof!:
smpic x(0) y(0) P:small
small x(50) y(50) P:
x(0) y(0) P:null

50px is the '#wall' margin, border is nowhere.

Take a look at the box model, the measurements your script returns are for the content area.

Thanks for your answer.

So you are saying the problem is in the script, in the way it calculates the absolute offset of the image (which has no border etc... itself) from the Top and the Left, using offsetTop() and offsetLeft()?

From javascript.com:
offsetTop: gets the vertical offset position of the current element relative to its offset container
offsetLeft: gets the horizontal offset position of the current element relative to its offset container

The function is called as xy = objabs(IMG);

Anybody?

http://www.webmaster-talk.com/javasc...ordinates.html