function brows_chk(){
  var ua,mode;
  ua = navigator.userAgent;
  if(ua.indexOf("MSN 6",0) >= 0){
    mode = "M6";
  }
  else if(ua.indexOf("MSIE 6",0) >= 0){
    mode = "I6";
  }
  else if(ua.indexOf("MSIE 5",0) >= 0){
    mode = "I5";
  }
  else if(ua.indexOf("MSIE 4",0) >= 0){
    mode = "I4";
  }
  else if(ua.indexOf("Netscape/7",0) >= 0){
    mode = "N7";
  }
  else if(ua.indexOf("Netscape6",0) >= 0){
    mode = "N6";
  }
  else if(ua.indexOf("Mozilla/4",0) >= 0){
    mode = "N4";
  }
  else{
    mode = "X";
  }
  return mode;
}