OK, I finished the design. When I disable development mode AND put CSS/JS to compress & minify AND open the Joomla cache from time to time the frontpage collapses, showing the menu on the left downwards/chashed.
I used this template on J1.5.x without any problem.
1) It can be a template problem
2) It can be a Jat3 problem
3) It can be a Joomla Cache problem. In fact although the caching is disabled, the Joomla cache was producing page items under cache, so need to delete them continuously during development.
Is this a known problem? My site does not work in full speed with these settings (except expires headers in .htaccess).
Here it is: http://www.adalarturizm.org
Thank you in advance.