function addEventHandler(selector, speed, opacityOut, opacityOver){
	$(selector).fadeTo(speed, opacityOut);
	
	$(selector).mouseover(function(event){
		$(this).fadeTo(speed, opacityOver);
	});
	
	$(selector).mouseout(function(event){
		$(this).fadeTo(speed, opacityOut);
	});
}


$(document).ready(function(){
	var selector = "img.opacity";
	var speed = "fast";	//"slow", "normal" ,"fast" の指定。または数値1とか　1=1/1000秒 数字の場合は " なし
	var opacityOut = 1;
	var opacityOver = 0.7;
	addEventHandler(selector, speed, opacityOut, opacityOver);
});