I have some more questions regarding this issue.

1) What is happening when I enable "content localization"?
It duplicates the pages/tabs and related modules/settings etc.
At some point, pages that belongs to X language is kept at some place, where is that place? at what sql table?

2) Is it possible to extend the portal template to include some custom sql scripts?

thanks,
umut

I didnt know the way that template portal is working! I tried to find details for this but I couldn't!
I checked the tabs table as you specified and realized that there is a field (CultureCode) for keeping language of the page. I add this to my portal template file for one of my pages for testing, then I also find the DNN\DesktopModules\Admin\Portals\portal.template.xsd file and add CultureCode to it(to satisfy the correctness of the template file) I HOPE that it is working automatically.
Unfortunately it is not, I created the new site succesfullt but without culturecode! where I can find the details of how portal template is working???