500 Internal Server Error, what should I do?

Question

htaccess

I did authorization and registration on the site, I decided to check and then bam and 500 Internal Server Error.

Internal Server Error
The server encountered an internal error or misconfiguration and was unable to complete your request.
Please contact the server administrator at [no address given] to inform them of the time this error occurred, and the actions you performed just before this error.
More information about this error may be available in the server error log.
Additionally, a 500 Internal Server Error error was encountered while trying to use an ErrorDocument to handle the request.

On the Internet, it was indicated that the matter was in .htaccess
. Here are its contents:

RewriteEngine on 
RewriteCond %{REQUEST_FILENAME}\.php -f 
RewriteRule ^(.*)$ $1.php
RewriteCond %{REQUEST_FILENAME}\.html -f 
RewriteRule ^(.*)$ $1.html

Answer 1

A syntax error in the PHP script that deals with this very "authorization and registration". For example.