Error: Feed failed! Causes may be (1) No data found for RSS feed http://b.hatena.ne.jp/keyword/%E5%AF%9D%E5%8F%96%E3%82%89%E3%82%8C?sort=hot&threshold=3&mode=rss; (2) There are no items are available for this feed; (3) The RSS feed does not validate.
Please verify that the URL http://b.hatena.ne.jp/keyword/%E5%AF%9D%E5%8F%96%E3%82%89%E3%82%8C?sort=hot&threshold=3&mode=rss works first in your browser and that the feed passes a validator test.