A good Content Management System allows the webmasters to update the entire site by making a change once in the admin that can carry over to all pages of a site.
This means one can change the menu, side bar, page bottom, site design, or other sections of his site all at one time. So while some webmasters are changing every page, others can have the task completed in matter of few minutes.
Includes, Style Sheets and Content Management Systems
For the do it yourself webmasters, or a professional web designers looking to easily improve update efficiency, there is a middle ground between plain HTML pages and full-blown CMS.
By simply using an include on sites, webmasters can allow the entire site to be updated with one change. Includes are files that are included in a web page with one line of code. This allows all pages with that file included to be updated by changing the include file one time.
Style sheets operate in a similar way as includes. One line of code calls a file capable of determining the look of text and graphics on the site. Entire site designs can be created with style sheets. Using style sheets allows webmasters to change the entire look and layout of the site by changing one file.