when i added new user in my ubuntu hosting and try to access the site, i got the message. i spent some time searching for the problem and solution. my first guess, there is problem with file permission in the home directory. read about unix/linux file permission on my site here.
i use this step to solve the problem.
1. check your webserver software, is it running well, or any warning message.
2. check the file and folder attribut of your site root directory
3. make sure your webserver can access the directory. modify file permission for your home directory including your public_html folder and home folder.
4. in my case, my apache can’t access my home directory, so i simply modify my home folder permission
chmod 755 /home/hosting
chmod 755 /home/hosting/public_html
and in my case, the problem solved.