The two main parts of a template are the content management code and the theme. These should be kept separate so that the theme can easily be changed without affecting the structure. For example, the styles should be defined in an external style sheet and not embedded in the HTML code of the pages. The structure of a website will be defined by a set of templates. It is good practise to make the templates modular rather than having page templates containing all the code for each page. This allows site-wide changes to be easily applied. For example, the footer may be mostly identical between pages.
Web site templates are also used for generating massive number of web pages by means of a schematic layout. Template based web designing is best when one requires building a site that has lots of pages and navigation link. It is ideal to use a web template if the site needs to be updated from time to time.