for what it's worth, I got pretty tired of seeing Site (Front-End) and Administrator (Back-end) over and over again. I don't think you need to refer to both names EVERY time. i found that quite annoying to me.
http://help.joomla.org/content/view/1626/196/inconsistant use of 'open source' and 'Open Source'
also, first line references 'Administrator's Manual' should this be 'Administor Manual'?
http://help.joomla.org/content/view/1627/196/Under 'How the Manual is Organized', item 4: 'The Apendices' -- the menu item says: 'Apendixes', also, 'Glossary' could be lower case.
Help Screens:
First sentance: missing a terminal point (period) after Joomla!.
last paragraph: first sentance, last word: Manual wouldn't need to be capitalized.
Other Help Resources:
second to last line, under help.joomla.org: Manual again doesn't need to be capitalized.
http://help.joomla.org/content/view/1628/196/inconsistant use of spacing between sections.
Powerful Extensions: it states: 'Seven default Components are part of the standard Joomla! installation' I would have liked to have seen a list here.
Powerful Extnesions: I think it would also be wise to direct people to a location to find extensions: extensions.joomla.org
http://help.joomla.org/content/view/1629/196/Overview: #2: should be 'Organize' not 'Organized'