Content Management Systems allow owners to rapidly change the content of their site.

Not all companies may be interested in doing so; If they have an "IT" department, it is easy to have the content taken care of and formatted properly. Small offices that don't have full time computer people on the other hand can save time and money using a CMS or Content Management System. Large companies may also be attracted to a CMS system because it is a WEB 2.0 application. -- the White house site is powered by drupal

Themes for different CMS systems

Wordpress, Durpal, Joomla are all CMS systems build on a PHP programing architecture. The "theme" or design structure is build into the PHP in the same basic process as building an HTML page. PHP files contain both the HTML and the program code. Most often the page is opened directly and then calls PHP functions to fill in the data. Another method is the PHP functions create the data and the theme php is then opened -- the data is available with this method in variables. Weebly, facebook, myspace, ning are also CMS systems but they can not be installed on ones own host; Weebly and Ning can both operate on different domains but the program itself exists on the application host's system -- new features can not be added -- other PHP applications (shopping carts, sales and support chat services ... ) can not be added. Low end web hosts compete in the same price as weebly and ning for providing an online hosting with your own domain name.

Mockups for CMS and PHP web applications

The mockup design process for PHP applications is for the most part the same as the process for any other type of page that is shown on the internet. Follow the Web sites start here link and be sure to specify which CMS or application needs the mockup. For a list of application see wsmithdesign - PHP - web applications site. For drupal specifically see San Diego Freelance Drupal Design

The most  advanced CMS systems are Drupal and Joomla - they both feature plug in options that include shopping carts and Web 2.0 applications.