@sonnyyu tried right now ! Same result...
http://yun.ip/ ==> open automatically http://yun.ip/cgi-bin/luci/webpanel/homepage
http://yun.ip/sd/ ==> open automatically the php files http://yun.ip/sd/index.php
but
http://yun.ip/keystore_manager_example/ ==> DOESN'T open the index.html file !! It returns the error "No such file or directory" ... I have to manually write:
http://yun.ip/keystore_manager_example/index.html for open the page !!!