http://www.profilepicture.co.uk/ajax-file-upload-xmlhttprequest-level-2/
http://www.ajaxf1.com/tutorial/ajax-file-upload-tutorial.html
http://www.ueder.net/2011/11/02/%E6%A8%A1%E6%8B%9Fajax%E6%97%A0%E5%88%B7%E6%96%B0%E7%9A%84%E6%96%87%E4%BB%B6%E4%B8%8A%E4%BC%A0%E5%8A%9F%E8%83%BD/
