>>>i have saw a website, during internet browsing, its extension is 'do'
>>>all files have do extension.
>>>
>>http://www.fileinfo.com/extension/do
>>?
>
>He probably wants to know what was used to write the website...which looks like Java + PHP ....I think.

Well the truth is that the file extension tells you nothing - all that matters is that the web server in question maps that particular extension to the right handler :-}