Hotspots with transparent image.

I am trying to make a hotspot on a map, with a partially transparent image as a rollover, but the image come up with a white bagground instead of a transparent, I tried to save the picture as a .png and .gif but nothing work.

Here is the code I am working with:

Html:

<div id="kort"><img src="billeder/europe/europe.png" alt="europe" width="550" height="566" border="0" usemap="#Map" id="Image1" />

    <map name="Map" id="Map">

      <area shape="poly" coords="388,119,373,77,343,103,315,151,297,207,297,259,328,253,359,196,353,168" href="#" onmouseover="MM_swapImage('Image1','','billeder/europe/sweden.gif',1)" onmouseout="MM_swapImgRestore()" />

    </map>

</div>




java script:

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];}
}