function category3Load(category1, category2){
	url = '/category.php?category_1_id=' + category1 + '&category_2_id=' + category2;
	
	var httpObj = createHttpRequest();
	httpObj.open( 'GET', url, true );
	
	httpObj.onreadystatechange = function(){
		if(httpObj.readyState == 4){
			on_loaded(httpObj);
		}
	}
	
	httpObj.send("dummy");
}

// コールバック関数
function on_loaded(obj){
	res = obj.responseText;
	
	document.getElementById('category3').innerHTML = res;
}