Looks like the 9 series of Antminers and maybe more use LightTPD web server software  in their control board software.
Found this after reading up on the fault I get  --  LightTPD Unauthorized

Appears that sometimes the web server is looking for id / password prior to moving on to the Antminer web pages.

Any one have any ideas of what the default LightTPD id and password might be as used in Antminers. I have tried all the options available using root and/or admin = no go.