As time elapses, the site gets uglier and uglier. Or at least not nearly as often as they should. A Content Management System is software which allows staff people to add, delete, and modify their web site's content easily and directly. I have written such a system myself. The whole system is web based.
Content is maintained through the use of HTML forms.
No special software is needed on the staff person's computer whatsoever. The interface is simple. Anybody who knows how to use a browser to surf the web can use the Content Management System with little to no training. Once somebody makes a change and hit's 'submit', the web site is updated with the new information immediately. This prevents the site from degrading in appearance over time.