How Search Engines Deliver Results Pages - How Search Engines Evaluate a Link
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There are many factors that go into judging the value of a link. I have space here to discuss only a few of the more important ones.
In my previous article, mentioned earlier, I discussed what search engines “see” when they encounter a hyperlink, and how they “think” about each part. I briefly discussed something called “anchor text.” This is one factor among many that search engines look at when they attempt to place a value on any particular link.
Anchor text is the visible characters or words that are clicked on to follow a hyperlink. For example, on a page talking about gaming consoles, let’s say you find the phrase “I’ve looked all over, but so far I’ve only found one place that keeps the Xbox360 consistently in stock.” If the last four words are a hyperlink, a web crawler seeing that phrase will assume that the page it links to – which could even be eBay – are described in some way by the phrase “Xbox360 consistently in stock.” Interestingly enough, if hundreds of thousands of sites think a particular page is relevant for a particular set of terms, and link using those words, a website could score high for those word even if they never appear anywhere on the site itself. (This fact may shed some light on the way Google ranks pages for terms such as “failure”).
The raw or global popularity of the site doing the linking, as rated by the number of links coming into the site, also weighs into the evaluation. For example, a link to your website from SEO Chat carries a certain amount of weight – but a link to your website from NYTimes.com carries a lot more weight. PageRank is actually designed to measure this, though it is often out of date (Google only updates PageRank in its toolbar every three to six months).
Not everyone is popular everywhere, and that’s also true of websites. Search engines have begun to notice “topical communities;” they used to exist as “webrings” (and some still do). These are sites that cover the same subject(s) and interlink with each other. In this case, a link from a site in a topical community may be weighed more heavily if it is linking to a page that covers its topic. If it is linking to a page that covers something irrelevant to its usual topic, the “vote” will not be rated as strongly.
The text directly surrounding a link – not the anchor text – often gets greater scrutiny, and weight, than the rest of the text on the page. So a link from inside an on-topic paragraph may pass along a stronger “vote” than a link from within a sidebar or footer.
The subject matter of the linking page also weighs into how strong of a “vote” that page casts for the page to which it links. I already hinted at that a couple of paragraphs ago when I mentioned topical communities. A page that discusses the same topic as the page it links to is going to cast a stronger vote than it would if the two pages covered very different topics. Incidentally, this is one reason that blogs have been powerful for conferring a good ranking in the SERPs – and why blogs themselves often score high in the SERPs. They freely link to other pages when they discuss topics relevant to those pages, and they freely link to each other.
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