Without links, the World Wide Web (WWW) would just be a collection of unrelated documents. Links provide structure and provide both implicit and explicit information in the aggregate. For example, if a web page is linked from many web sites, it usually implies that it is a more important page than one that has fewer incoming links. Moreover, if the anchor text of those links contains the word “cookie,” this indicates to search engines that the cited page is about cookies.
Links assign value to web pages, and as a result they have a fundamental role in search engine optimization. This book frequently references a concept called URL equity or link equity. Link equity is defined as the equity, or value, transferred to another URL by a particular link. For clarity, we will use the term link equity when we refer to the assigning or transferring of equity, and URL equity when we refer to the actual equity contained by a given URL.
Among all the factors that search engines take into consideration when ranking web sites, link equity has become paramount. It is also important for other reasons, as we will make clear. Link equity comes in the following forms:
1. Search engine ranking equity. Modern search engines use the quantity and quality of links to a particular URL as a metric for its quality, relevance, and usefulness. A web site that scores well in this regard will rank better. Thus, the URL contains an economic value in tandem with the content that it contains. That, in turn, comprises its URL equity. If the content is moved to a new URL, the old URL will eventually be removed from a search engine index. However, doing so alone will not result in transference of the said equity, unless all the incoming links are changed to target the new location on the web sites that contain the links (needless to say, this is not likely to be a successful endeavor). The solution is to inform the search engines about the change using redirects, which would also result in equity transference. Without a proper redirect, there is no way for a search engine to know that the links are associated with the new URL, and the URL equity is thusly entirely lost.
2. Bookmark equity. Users will often bookmark useful URLs in their browsers, and more recently in social bookmarking web sites. Moving content to a new URL will forgo the traffic resulting from these bookmarks unless a redirect is used to inform the browser that the content has moved. Without a redirect, a user will likely receive an error message stating that the content is not available.
3. Direct citation equity. Last but not least, other sites may cite and link to URLs on your web site. That may drive a significant amount of traffic to your web site in itself. Moving content to a new URL will forgo the traffic resulting from these links unless a redirect is used to inform the browser that the content has moved.
Therefore, before changing any URLs, log files or web analytics should be consulted. One must understand the value in a URL. Web analytics are particularly useful in this case because the information is provided in an easy, understandable, summarized format. If a URL must be changed, one may want to employ a 301-redirect. This will transfer the equity in all three cases. Redirects are discussed at length in Chapter 4, “Content Relocation and HTTP Status Codes.”