I get Internal server error while altering the Permalink in wordpress. Things I did was

I transformed "Custom Structure" under Permalink configurations and gave /%category%/%postname%/

It requested me to place b .htaccess using the following content:

<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase ./
RewriteRule ^index\.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . ./index.php [L]
</IfModule>

Then my website become inaccessible i get Internal server error. I've my mod_rewrite enabled.

Any assistance is greatly appreciated. Thanks ahead of time.