This javascript functions in IE but not Firefox, can anyone tell me why?

function showOffset(object,x,y) {

if (document.layers && document.layers[object]) {

document.layers[object].left += x;

document.layers[object].top += y;

document.layers[object].visibility = 'visible';

}

else if (document.all) {

document.all[object].style.posLeft = document.all[object].offsetLeft + x;

document.all[object].style.posTop = document.all[object].offsetTop + y;

document.all[object].style.visibility = 'visible';

}

}



function hideOffset(object,x,y) {

if (document.layers && document.layers[object]) {

document.layers[object].visibility = 'hidden';

document.layers[object].left -= x;

document.layers[object].top -= y;

}

else if (document.all) {

document.all[object].style.visibility = 'hidden';

document.all[object].style.posLeft -= x;

document.all[object].style.posTop -= y;

}

}

Here is the html and css...

<style type="text/css">
.popup{font-family: Arial, Georgia, Sans-serif;
font-size: 16pt;
position: absolute;
z-index: 2;
font-weight: 600;
font-style: normal;
text-decoration: none;
text-transform: none;
font-variant: normal;
color: #FFFFFF;
background: #999933;
border: 3px groove #FFFFF0;
padding: 5px;
visibility: hidden;}

</style>

<a href="../maps_pdf/geologic/24k_maps/Amity.pdf" target="_blank" onMouseOver="showOffset('quad282',26,317)" onMouseOut="hideOffset('quad282',26,317)">Amity</a><br>

<map name="HotSpringQuads" id="HotSpringQuads">

<span id="quad282" class="popup">
Amity</span>
<area shape="poly" coords="16,283,95,284,95,385,15,386" href="../maps_pdf/geologic/24k_maps/Amity.pdf" target="_blank" alt="Amity" onMouseOver="showOffset('quad282',26,317)" onMouseOut="hideOffset('quad282',26,317)" />

</map>

<img src="../dgm_browse/HotSpring.jpg"
width="600" height="600" border="0" usemap="#HotSpringQuads" />


Any help would be appreciated! I'm new at this.

Seems like a very old script, it checks if the browser supports either "document.layers" or "document.all", AFAIK the former was only supported by Netscape4 while the latter is not supported by Firefox.

What's the purpose of the script, just showing/hiding the box called "Amity"?