Continuing on from yesterday, Web/Graphic designers plot out the website navigation using a simple form of sitemap, please refer to uploaded example. Basically this acts as an aid in the event of a problem with the linking of all the pages within the site. The plan is to have all the pages linking with each other but sometimes this can go wrong and the map is a paper version of the navigation you can refer back to, to help you re-establish those broken. This is not quite so crucial if the site only consists of a few pages, as it is fairly easy to backtrack and solve the problem. But say for instance you were building a site on the scale of Amazon, this map would be a life line in establishing any broken links.
Another form of sitemap is used by Google, Yahoo and other search engine providers. This is a page which is attached to the back end of your website, you provide a list of pages within the site and a link to each of the pages. When the site is submitted to say, Google for optimization ( Google crawls the site with their crawler Googlebot, which is searching for keywords and relevant information relating to your site, the more information it can find the further the site moves up the rankings) sometimes Googlebot doesn’t always crawl all the pages, as there could be missing or broken links. in this case if the sitemap page has been included, Googlebot will crawl this page seeking the information.
Both images are my own