Internal Links are hyperlinks that point at (target) the same domain as the domain that the link exists on (source). In layman’s terms, an internal link is one that points to another page on the same website.
<a href="http://www.same-domain.com/" title="Keyword Text">Keyword Text</a>
Use descriptive keywords in anchor text that give a sense of the topic or keywords the source page is trying to target.
Internal links are useful for three reasons:
- They allow users to navigate a website.
- They help establish information hierarchy for the given website.
- They help spread link juice (ranking power) around websites.
Reasons why pages might not be reachable, and thus, may not be indexed:
Links in Submission-Required Forms
Forms can include elements as basic as a drop–down menu or elements as complex as a full–blown survey. In either case, search spiders will not attempt to “submit” forms and thus, any content or links that would be accessible via a form are invisible to the engines.
Links Only Accessible Through Internal Search Boxes
Spiders will not attempt to perform searches to find content, and thus, it’s estimated that millions of pages are hidden behind completely inaccessible internal search box walls.
Links in Flash, Java, or Other Plug-Ins
Any links embedded inside Flash, Java applets, and other plug-ins are usually inaccessible to search engines.
Links Pointing to Pages Blocked by the Meta Robots Tag or Robots.txt
The Meta Robots tag and the robots.txt file both allow a site owner to restrict spider access to a page.
Links on pages with Hundreds or Thousands of Links
The search engines all have a rough crawl limit of 150 links per page before they may stop spidering additional pages linked to from the original page. This limit is somewhat flexible, and particularly important pages may have upwards of 200 or even 250 links followed, but in general practice, it’s wise to limit the number of links on any given page to 150 or risk losing the ability to have additional pages crawled.
Links in Frames or I-Frames
Technically, links in both frames and I-Frames are crawlable.
Links can have additional attributes applied to them, but the engines ignore nearly all of these, with the important exception of the