function initRollovers() {
if (!document.getElementById) return

var aPreLoad = new Array();
var sTempSrc;
var aImages = document.getElementsByTagName('img');

for (var i = 0; i < aImages.length; i++) {
if (aImages[i].className == 'imgover') {
var src = aImages[i].getAttribute('src');
var ftype = src.substring(src.lastIndexOf('.'), src.length);
var hsrc = src.replace(ftype, '_on'+ftype);

aImages[i].setAttribute('hsrc', hsrc);

aPreLoad[i] = new Image();
aPreLoad[i].src = hsrc;

aImages[i].onmouseover = function() {
sTempSrc = this.getAttribute('src');
this.setAttribute('src', this.getAttribute('hsrc'));
}

aImages[i].onmouseout = function() {
if (!sTempSrc) sTempSrc = this.getAttribute('src').replace('_on'+ftype, ftype);
this.setAttribute('src', sTempSrc);
}
}
}
}

if (window.addEventListener) {  /* Firefox,Safari,Opera */  
    window.addEventListener("load", initRollovers, false);  
}   
 else if (window.attachEvent) {  /* IE4, IE5, IE6, IE7 */  
     window.attachEvent("onload", initRollovers);  
}      
 else if (document.getElementById || document.all) { /* その他DOM準拠 */  
     window.onload = initRollovers;  
}