Security

I was looking around and went to security and found this message there.
WordPress version: 2.5.1 You have the latest stable version of WordPress.
Your table prefix should not be wp_. Click here to change it.
Your WordPress version is successfully hidden.
WordPress DB Errors turned off.
WP ID META tag removed form WordPress core
“admin” user exists.
The file .htaccess does not exist in wp-admin/.

I checked and htaccess is there and I don’t know enough to change the rest of it.