Indexation component and search engine optimization

Index Component: Links and Navigation

This section examines how to build links that search engine spiders can follow.
A good navigation structure makes it easier for search engines spiders and users to browse your web site. It’s easy to understand because it’s just good common sense. If it is easy for users to navigate your site, they will most likely return. If it is easy for search engines to follow your links, it is more likely that they will index many of your web pages. The more web pages you have indexed, the more likely it is that one of them will be found in a search, thus leading a visitor to your web site. How many of your web pages are indexed by a particularly search engine is called “search engine saturation”.

Use hyperlinking that search engines can follow

Search engine spiders can't follow every kind of link that webmasters use. In fact, the only kind of hyperlinks that you can be certain all search engine spiders can and will follow are standard text-based links.
In HTML code, text-based links are written like this:
< a href="http://www.domain.com">Link text

The link will look like this on a web page: Link text

All other forms of links can pose a problem for search engine spiders.
Tip: Use a html editor
If you are using a WYSIWYG editor or content management system, it will usually output the correct HTML code for you when you insert a text link. You can verify that it is indeed a text link by highlighting the link text in your browser. If you can highlight it letter by letter like most other text on a web page, and you can copy and paste it into a text editor like notepad or Word, then you should be safe.

Image maps and navigation buttons

Sometimes designers want to use graphics for navigational links. Two common ways of making graphical links are very different: image maps and navigation buttons.
Image maps can have different areas of one image linking to different web pages frequently used to build page elements like top and side navigation bars or country maps. Most search engines do not read image maps, so you should always add additional text-based links on each page for search engine spiders to follow. The text-based links will also be good for visitors who do not use a graphics-capable browser or visitors who surf with graphics turned off to save bandwidth.
Navigation buttons are single images that each link to a specific web page. Most search engines spiders will follow navigation button links. However, if you want to be absolutely sure that all search engines can and will follow all of your links, we still recommend adding pure text-based links in addition to any kind of graphical links. In addition, text links can have keywords within the hyperlink while navigation button links cannot.
See also the Text Component section.

Flash, Macromedia and Java Applets

Flash, Shockwave, and Java Applets have something in common: They all require the user to have a special program installed on their computer to open and play the files. Most new browsers come with the necessary programs installed to play the most common file types. However, search engine spiders usually do not open such files.
We recommend that you do not build your navigation links using any of these techniques. If you do, you should only serve the high-tech version of your web site to users that have the right plug-ins installed, and have a low-tech version ready for all other users. The low-tech version should include regular text-based links, which will work well with search engine spiders as well as users that do not have these plug-ins installed.

Tip: use a sitemap
If you are using techniques to present navigational links that require the user to have a certain plug-in installed, you can add standard navigation text-links for the search engine spiders to follow in the footer of each web page. Also, site maps with a complete overview of all pages with links can help both your visitor and the spider.

Java Script and DHTML

Search engine spiders do not read JavaScript!