It should be friendly not only to the human eye, but also to search-engine spiders—programs that crawl the Web looking for up-to-date information.
A site’s structure can make a big difference in how easily a spider can crawl it. Web addresses that use keywords related to the content of the page generally help a search engine better correlate them with the site. For example: www.yourwebsite.com/keyword/filename.html. The closer the keyword is to your homepage in the Web address, the more relevant a search engine will consider the page to be for that keyword, and the more likely the search engine will be to give your site a better ranking.
Another consideration is where content is placed on the page. Spiders read pages starting at the top left corner of a page, so pages, keyword links to content that’s especially important for search engines to see should be moved there.