function rollover(id,src)
	{
		document.getElementById(id).src=src;
	}

// png rollover
function imgSwap(id)
{
	var oImg = document.getElementById(id);
   	var strOver  = "_on"    // image to be used with mouse over
   	var strOff = "_off"     // normal image
   	var strImg = oImg.src
   	if (strImg.indexOf(strOver) != -1) 
      oImg.src = strImg.replace(strOver,strOff)
   	else
      oImg.src = strImg.replace(strOff,strOver)
}