Hi baijianpeng and Gary:
Sorry for the confusion, maybe I didn't write clearly at the documentation when to use this modified version of .htaccess
This is meant (and necessary for rewrite rules to work on all your sites) when you use several tikis in the same host based on a MultiTiki installation, and each individual Tiki is accessed as subdirectories of the same domain.
Examples (real cases):
All of them, in our case, use the same file tree, the same single installation of files on the server, with one mysql db for each tiki (i.e., "multitiki on subdirs").
On the server, each of those subdirs (/home/htdocs/cursos/, /home/htdocs/euromovements/, ...) are just symlinks to the same directory where tiki is installed (/home/httpd/tiki19/ for instance), and that tiki installation is the one which has that modified version of .htaccess
Sorry for the previous confusion. I hope it's clearer nowadays.
Ask again if still in doubt.