Every page served by the CMS is composed by three independent elements that sum up to define the final page's appearance and functionality: template, style and content.
The template is the "skeleton" of each page. It contains the basic header, side-bars and footer structure with a place-holder for the content. Each page may use a different template (you may have as many templates as you want installed).
The style is the set of look and feel configurations you apply to the entire site as well.
For a smooth CMS experience, make sure your templates and content use a compatible set of id and classes contemplated by your style settings along your site.