Error 404 on well published pages

Hi everybody,

on my website http://www.nutritionalmovement.com I had published some months ago all the page I needed and they worked properly till today.

For example http://nutritionalmovement.com/contact/
or one of the most important pages like http://nutritionalmovement.com/categorie/ give me 404 error Page not found.

I have tried also to rebuild this page into a new one and till I was on a draft mode it worked, than, after publish, there is absolutely no way to see it.

This drawback causes me a lot of problems because this is the main page to navigate my site.

May you help me?

Many thanks

Francesca