取消超連結元素預設的動作

http://blog.xuite.net/vexed/tech/25193980-%E7%84%A1%E4%BD%9C%E7%94%A8%E9%80%A3%E7%B5%90%E8%A9%B2%E5%AF%AB+%3Ca+href%3D%22%23%22+%E9%82%84%E6%98%AF+%3Ca+href%3D%22javascript%3A+void(0)%22