var on1 = new Image;
        on1.src ="images/but1a.gif";
        var off1 = new Image;
        off1.src="images/but1.gif";

        var on2 = new Image;
        on2.src ="images/but2a.gif";
        var off2 = new Image;
        off2.src="images/but2.gif";

        var on3 = new Image;
        on3.src ="images/but3a.gif";
        var off3 = new Image;
        off3.src="images/but3.gif";

        var on4 = new Image;
        on4.src ="images/but4a.gif";
        var off4 = new Image;
        off4.src="images/but4.gif";
       
        var on5 = new Image;
        on5.src ="images/but5a.gif";
        var off5 = new Image;
        off5.src="images/but5.gif";

        var on6 = new Image;
        on6.src ="images/but6a.gif";
        var off6 = new Image;
        off6.src="images/but6.gif";




function mouse_over(imageNum) {
  var iNum;
  var name;
  var iname;
  iNum = parseInt(imageNum);
  name = "i"+iNum;
  iname = "on"+iNum+".src";
  document[name].src = eval(iname);     
  return true;
}

function mouse_out(imageNum) {
  var name;
  var iname;
  name = "i"+imageNum;
  iname = "off"+imageNum+".src";
  document [name].src = eval(iname);
  return true;
}