Wireframes
are a basic visual guide used to suggest the layout and
placement of the main design elements on a web page. Because
of this they are usually completed before any artwork is developed.
Wireframes allow for the development of variations of a layout whilst
maintaining design consistency throughout the site. Wireframes are
often black and white, line diagrams, they don't contain any 'look and
feel' and are there to test the structure, navigation and generic
conventions of the site.