var isIE = isIE = (document.documentElement.getAttribute("style") == document.documentElement.style);

var preloadImg = new Object();
var preNum = 0;

window.onload = function(){
	btnOverEvent();
}

function setEvent(obj,eventType,func){
	if(isIE) {
		obj.setAttribute(eventType,new Function(func));
	} else {
		obj.setAttribute(eventType,func);
	}
}

var btnOverEvent = function(){
	var images = document.getElementsByTagName('img');
	for(var i = 0,num = images.length;i < num; i++){
		var img = images[i];
		var imgSrc = img.src;
		if(imgSrc.indexOf('_n.') > -1 && img.parentNode.href){
			var newImgSrc = imgSrc.split('_n.')[0] + '_o.' + imgSrc.split('_n.')[1];

			preloadImg[preNum] = new Image();
			preloadImg[preNum].src = newImgSrc;

			var funcOnImg = 'changeImg(this,\'' + newImgSrc + '\')\;return false\;';
			var funcOutImg = 'changeImg(this,\'' + imgSrc + '\')\;return false\;';
			
			setEvent(img.parentNode,'onmouseover',funcOnImg);
			setEvent(img.parentNode,'onmouseout',funcOutImg);
			preNum++
		}
	}
}


function changeImg(eventAnchor,imgSrc){
	eventAnchor.getElementsByTagName('img')[0].src = imgSrc;
}


function insertBackBtn(){
	document.write('<input type="button" onClick="history.back()" value="戻る" />');
}