Ok, so I have to migrate my users. Thanks for your answer!

Thanks for your answer.
For the users, my sub site (in production) has some users already registered. Is there a way Mightysites fetch these users in the main site?

Thanks.

Hello, I have actually 2 Joomla 2.5 websites: - My main website at http://www.mysite.com (which is actually under construction) - The second one at http://radio.mysite.com (sub domain which is in production, installed in a folder: root/radio/). I plan to open 3 other websites in this little network ...