rollover sur plusieurs image map

<script type="text/JavaScript">// <![CDATA[
    function MM_preloadImages() { //v3.0
        var d=document; if(d.images){ if(!d.MM_p) d.MM_p=new Array();
                                      var i,j=d.MM_p.length,a=MM_preloadImages.arguments; for(i=0; i<a.length; i++)
                                          if (a[i].indexOf("#")!=0){ d.MM_p[j]=new Image; d.MM_p[j++].src=a[i];}}
    }
    function MM_swapImgRestore() { //v3.0
        var i,x,a=document.MM_sr; for(i=0;a&&i<a.length&&(x=a[i])&&x.oSrc;i++) x.src=x.oSrc;
    }
    function MM_findObj(n, d) { //v4.01
        var p,i,x;  if(!d) d=document; if((p=n.indexOf("?"))>0&&parent.frames.length) {
            d=parent.frames[n.substring(p+1)].document; n=n.substring(0,p);}
        if(!(x=d[n])&&d.all) x=d.all[n]; for (i=0;!x&&i<d.forms.length;i++) x=d.forms[i][n];
        for(i=0;!x&&d.layers&&i<d.layers.length;i++) x=MM_findObj(n,d.layers[i].document);
        if(!x && d.getElementById) x=d.getElementById(n); return x;
    }
    function MM_swapImage() { //v3.0
        var i,j=0,x,a=MM_swapImage.arguments; document.MM_sr=new Array; for(i=0;i<(a.length-2);i+=3)
            if ((x=MM_findObj(a[i]))!=null){document.MM_sr[j++]=x; if(!x.oSrc) x.oSrc=x.src; x.src=a[i+2];}
    }
    // ]]></script>
<div id="right">
    <div class="custom_btn"><img usemap="#Map" id="image_origine" src="images/btn_1_on.png" width="170" height="166" />&nbsp;
        <map name="Map" id="Map">
            <area shape="poly" coords="82,23,82,80,130,109,138,92,138,73,132,49,118,34,99,24,81,23" href="test.html" class="map2" onmouseover="MM_swapImage('image_origine','','images/btn_1_on_2_over.png',1)" onmouseout="MM_swapImgRestore()" />
            <area shape="poly" coords="32,111,53,131,81,138,107,131,129,110,82,82,33,111" href="test.html" class="map3" onmouseover="MM_swapImage('image_origine','','images/btn_1_on_3_over.png',1)" onmouseout="MM_swapImgRestore()" />
 
        </map>
    </div>
</div>