/* USER_AGENT check start  */
// NN4, NN5(Netscape 6+, Mozilla 1+?), IE4(IE4+), Unknown
g_USER_AGENT = getAgent();

// return NN4, NN5(Netscape 6+, Mozilla 1+?), IE4, IE5(IE5+), Unknown
function getAgent(){
  var userAgent = navigator.userAgent;
  var charIndex;
  var majorVersion;

  charIndex = userAgent.indexOf("MSIE");
  if(charIndex){
    majorVersion = userAgent.charAt(charIndex + 4 + 1);
    if(majorVersion > 4){
      return("IE5");
    }
    else if(majorVersion == 4){
      return("IE4");
    }
  }

  charIndex = userAgent.indexOf("Mozilla");
  majorVersion = userAgent.charAt(charIndex + 7 + 1);
  if(majorVersion > 4){
    return("NN5");
  }
  else if(majorVersion == 4){
    return("NN4");
  }

  return("Unknown");
}
/* USER_AGENT check end  */

function getWindowYOffset(){
  if(g_USER_AGENT == "IE5" || g_USER_AGENT == "IE4"){
    return document.body.scrollTop;
  }else if(g_USER_AGENT == "NN5" || g_USER_AGENT == "NN4"){
    return window.pageYOffset;
  }else{
    return 0;
  }
}

var waitTimer;
function jumpTo(dstY, srcY, scrollRate, waitMillSec) {
  if(waitTimer){
    clearTimeout(waitTimer);
  }
  if( ! dstY || dstY < 0 ){
    dstY = 0;
  }
  if( ! srcY ){
    srcY = 0 + getWindowYOffset();
  }
  if( ! scrollRate ){
    scrollRate = 10;
  }
  if( ! waitMillSec ){
    waitMillSec = 20;
  }

  srcY += (dstY - getWindowYOffset()) / scrollRate;
  if(srcY < 0){
    srcY = 0;
  }
  posY = Math.floor(srcY);
  window.scrollTo(0, posY);

  if(posY != dstY){
    waitTimer = setTimeout("jumpTo("+ dstY +", "+ srcY +", "+ scrollRate +", "+ waitMillSec +")", waitMillSec);
  }
  else if(posY == dstY){
    clearTimeout(waitTimer);
  }
  else if(posY < 1){
    window.scroll(0, 0);
  }
}

function toTop(){
  jumpTo(0, 0, 10, 0);
}