Sometimes you need to change some parameters to your apache virtual host. Then, when you need to check the changes, in plesk you'd probably will have to execute the next command to see the changes:

/usr/local/psa/admin/sbin/httpdmng --reconfigure-domain exampledomain.com

Otherwise, restarting apache (/etc/init/apache2 restart) could not make the trick.

I allways forgot this little trick... never more, because Programadores Web will remind it me :-).