function initRollOvers() {
 if (!document.getElementById){
  return;
 }

 var preLoads = new Array();
 var allImages = document.getElementsByTagName('img');

 for (var i = 0; i < allImages.length; i++) {    
  if (allImages[i].className == 'pbRollover') {
   var src = allImages[i].getAttribute('src');
   var ftype = src.substring(src.lastIndexOf('.'), src.length);
   var oSrc = src.replace(ftype, 'Hv'+ftype);

   //-- スワップ元、スワップ先画像の登録
   allImages[i].setAttribute('pSrc', src);
   allImages[i].setAttribute('oSrc', oSrc);

    //-- イメージのプリロード
   preLoads[i] = new Image();
   preLoads[i].src = oSrc;

   //-- イベントの設定
   allImages[i].onmouseover = function() {
    this.setAttribute('src', this.getAttribute('oSrc'));
   }
   allImages[i].onmouseout = function() {
    this.setAttribute('src', this.getAttribute('pSrc'));
   }
  }
 }
}

function addOnload(func){
 if ( typeof window.addEventListener != "undefined" ){
  window.addEventListener( "load", func, false );
 }else if ( typeof window.attachEvent != "undefined" ) {
  window.attachEvent( "onload", func );
 }else{
  if ( window.onload != null ){
   var oldOnload = window.onload;
   window.onload = function ( e ) {
   oldOnload( e );
   window[func]();
  };
 }else
  window.onload = func;
 }
}
addOnload(initRollOvers);