@Sakin, I got it.
Someone just did a copy/paste on posts from our older web and it was not responsive at all. Found that every post began with a <div style="margin: 0 75px">
and just changed 75px with a % value, so I can still give som custom margins.
Thanks for your help, http://www.farma-ceutics.com is already finished (but waiting for a multi-site for other languages).
Regards