var NS4 = (navigator.appName=="Netscape") && (navigator.appVersion.indexOf('4.')==0); 
var IE4 = (navigator.appName=="Microsoft Internet Explorer") && ((navigator.appVersion.indexOf('4.')==0) || (navigator.appVersion.indexOf('5.')==0)); 
var VER4 = NS4 || IE4; 

function ChgBtnImage(Btn, FileName)
 {
  Btn.src = "images/" + FileName;
  return false;
 };