Removes version of WordPress in all areas

I’m using firefox 16.0.2. When I click on the properties page, the following appears (when I’m not in admin):
text / html charset = UTF-8
WordPress 5807

When I’m in admin, clicking on the properties page, the following appears:
text / html charset = UTF-8

Am I doing something wrong? Is that so?

http://wordpress.org/extend/plugins/secure-wordpress/