how to put username after domain name

[eluser]CroNiX[/eluser]
You can do this with routes, but it would be a bit complicated because you'd be breaking the default way CI maps the url to a controller/method (there would be no controller/method in the url). So you'd need to create a route for every controller that you use, and then at the very end of them have a catch-all route like
$route['(:any)'] = 'controller/method/$1';
Where it would pass whatever was after the domain name in the URL to the 'controller/method' that you want to use.

You need all of the other controllers mapped before that route though, or no other controller could be accessed since it will send everything to that one controller that you want to use to display the profile (or whatever).