How to fix http 404 error?

I have a CPANEL ERROR when I use the tilde to acess a site it goes through but when I remove it I get a 404 error  e.g http://192.168.0.1/~Username/index.php -> works fine while  http://mysite.com/index.php -> does not work it gives me a 404 not found Anyone had n solved this before?

• Answer:

  If the user does not have a dedicated IP address this is the way it works. The IP address goes to the default site on the server, where index.php does not exist. The ~User is using mod_userdir which actually redirects it to the correct user dir.