The first thing you should consider before you start building your web pages is the website’s navigation and structure. It is better to spend a bit of time designing the structure as once you have implemented one method it is not so easy usually to change things and certainly it is not cost or time effective at all. It is highly recommendable to keep your design as flat as possible. You do not want a deep design with many levels by any means. Certainly you will not place all your content in the root directory for optimal results; however you should make sure the site’s design goes no deeper than two or three levels.
For instance, the following URL is a flat directory structure with two levels: http://www.Mydomain.com/Page1/Page2.html .
The example below is generally not a good practice:
http://www.Mydomain.com/Page1/Page2/Page3/Page4.html
Moreover, your site will be more user friendly, if you keep pages with similar subject in the same directory.
There are several reasons for keeping a flat directory structure, but the most important of them, is that search engines sometimes do not perform deep crawling. Sometimes, search engines are set to crawl, a specific website, only to a certain depth. This can happen if the site is new or because the site is too many levels deep. So for instance, in a new website, the search engine will probably crawl only to a depth of 2, so in a deep website structure, some pages will not be indexed at all. Of course, you understand that the pages that are not indexed do not exist for the search engines. The engines will never find and rank your content! On the other hand, when you have the flat directory structure all the pages are crawled and search engines fully understand the structure of your website.
Sitemaps
After you have finished your website, it is exceptionally important to create a sitemap. A sitemap has a link for every page that exists inside a website from one single page. With the sitemap’s help a search engine or a visitor can go to any other page on a website from this single page. Bear in mind that if you link to the sitemap from every single page on your website then the result is similar to interlinking all of your web-pages with each other. Having a sitemap means that you help search engines crawl and index every page on your website. Also another tip for you is this: The best way to get indexed is through link building. Google provides a free program named Google Sitemaps that you can use to help their crawler find out what pages are on your site. This program will also tell you what Google searches send you the most visitors as well as if their bot is having any crawling problem with your site.
Maybe you think that you can create a sitemap and stop worrying about your site’s structure, but this is completely wrong. As mentioned before, search engines frequently crawl only to a certain depth, so links on your sitemap like the following: http://www.Mydomain.com/Page1/Page2/Page3/Page4.html will be ignored because the depth of the web-page is bigger than the search engines maximum crawl depth.
I hope this article has helped you understand how to create a good, search engine friendly, site structure.

Author's Bio: 

Manolis Skoras has highly developed technical skills in problem identification and implementation of effective IT solutions. Comfortable with analyzing and understanding complex network and system environments, working under time pressure and with a proven track record in IT Consulting, IT Training, IT Project Management. Delivered more than 10.000 technical training hours. IT Study Guides -Certification Training