When I look at the page source meta description is: "Joomla! - the dynamic portal engine and content management system"

This will place the same description on every menu item that is not looking at a specific article, creating duplicate keywords that search engines DO NOT like.

 

Log on to your sites administrator control panel.

Go to Site | Global configuration, under the "site" tab you will see:

metadata settings > Global Site Meta Description:
metadata settings > Global Site Meta Keywords:

Clear all text from these fields and save.