ISPConfig has disabled .htaccess per default. You need add this directive to httpd.conf:
And all your .htaccess will star work. BUT Till said me:
Setting these things in .htaccess is not allowed for security reasons
as it would allow poaple e.g. to
enable disabled functions too. Instead, just add the line:
php_value memory_limit 128M
in the apache directives field in ispconfig.
Php disable some directives for only setup in php.ini, i think allow .htaccess is not a security reason, ISPConfig has other security problems more importants.
For example 'Magento' need change some php directives in .htaccess, but its disabled, i think is very hard for the user change .htaccess from the control panel every time he need change it, or install new CMS, etc...