Enable Apache2 mod_headers and mod_expires on Debian 7

Enable Apache2 mod_headers & mod_expires on

To increase PageSpeed: Leverage browser caching.

enable mod_headers:

#a2enmod headers
Enabling module headers
To activate the new configuration, you need to run:
service apache2 restart

enable mod_expires:

#a2enmod expires
Enabling module expires
To activate the new configuration, you need to run:
service apache2 restart

Then restart Apache server to make these changes effective

#service apache2 restart