Problems with .htaccess

[Sortes]

Because if I go up the file htaccess, I have error 500?

Internal Server Error

The server encountered an internal error or misconfiguration and was unable to complete your request.
Please contact the server administrator, webmaster@esmiforo.com and inform them of the time the error occurred, and anything you might have done that may have caused the error.
More information about this error may be available in the server error log.
Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request.
Apache Server at www.esmiforo.com Port 80

[NightStorm]

What does the site's error_log say? It'll most often include a more specific reason why the 500 was tossed up. This could be anything from php flags in an htaccess on a server running phpSuExec, to improper ownership (again, when running phpSuExec, proper ownership is critical), to an improperly formatted htaccess file (bad line breaks, or invalid characters being added). The last one can happen if the file is not uploaded in the proper format. It may also be a conflict with a mod_security rule.
Basically, the 500 error can be all sorts of things, and the best way to start tracking it down is to check the error log.

[Derek]

Also, make sure your host supports .htaccess and mod_rewrite.

Derek