Search Engine Marketing, Inc.: Driving Search Traffic to Your Companys Web Site [Electronic resources] نسخه متنی

Ranking the Matches

Merely displaying the list of all the pages that contain the words in the query is not much help when there are more than a dozen pages. And with Web search, that is almost always the case. So, one of the most important parts of a search engine is the ranking algorithmthe part of the search engine that decides which pages show up at the top of the results list.

Both organic results and paid results must be ranked, but the organic ranking algorithm is by far the most complicated, so we tackle that first.

Ranking Organic Search Matches

A search engine's organic ranking algorithm is one of the trickiest parts of designing a search engine, so let's start by examining the simplest kind of ranking algorithm.Ranking is just another word for sorting, the act of collating results into a certain order. Shopping search engines typically use simple ranking algorithms that the searcher can choose. When the searcher is looking for a product to buy, the shopping search engine might start by ordering the results by price (lowest to highest), but the searcher can decide to sort the list by other columns, such as availability (in stock, within one week, and so on), or any other features of the product.relevance, the degree to which the pages match the subject of the query.keyword. Unfortunately, keyword is a somewhat ambiguous termat times it means an individual word in a query, but at other times it denotes the entire query. We use keyword or query to refer to the entire string of words a searcher types, but refer to a word or a search term when it is important to emphasize an individual search query word.

Keyword Density

Perhaps the simplest thing search engines look for is how many of the terms in the search query are actually found on the page. All other things being equal, pages that have more of the terms in the query (some search engines require all of the important terms) tend to rank higher.Keyword density, also known as keyword weight, is critical. In the old days of search, the more frequently the terms occurred on the page, the better. A page with a term frequency of ten occurrences for the word glaucoma was considered better than one with two, when that is what a searcher is looking for.keyword proximity (the terms are closer together) are often better than those that contain the terms separated by a few words, or worse, a few paragraphs. Web search engines work hard to find as many of the terms in the query as possible, with as many occurrences on the page as possible (up to that magical 7 percent threshold), as close to each other as possible. As you might imagine, it is critical for you, the search marketer, to write your pages using these keywords and phrases. We teach you how to do that in Chapter 12, "Optimize Your Content."

Keyword Prominence

Besides knowing that a page contains the words in a search query, isn't it important to know where they appear on the page? You better believe it. All other things being equal, pages where query terms appear in important places, such as the page title, tend to rank higher than pages where the terms are buried at the page bottom. Pages that feature query words in titles and initial paragraphs are said to have high keyword prominence, because the keywords appear in more prominent places than on other pages.

Why do search engines emphasize keyword prominence? Because search engines are, at heart, pattern-matching machines. They are tuned to recognize various patterns associated with pages that strongly match queriespages with a pattern of keyword matches in prominent places are stronger matches than others.

So how does the search engine evaluate the prominence of terms it finds in various parts of the page? Here are the major categories, which are also depicted in Figure 2-4:

Title.
This is the most important part of the Web page to a search engine. The title is what displays in the search results page, and it is also shown in the window title for the browser. You can think of a Web page's title as similar to the title of a magazine article, which usually strongly indicates what the entire article is about.

Headings and emphasized text.
Most search engines give more weight to terms found in bold headings, and to italicized or colored text, assuming that these are more important occurrences of the terms. Headings are most similar to bold section headings inside a magazine article that break up the running text and indicate what the paragraphs below are about.

Body text.
Body text includes all the words that appear on the page, but body text that appears closer to the top of the page is considered more important than text found in the middle or at the bottom of the page. Pictures on the page also contain alternate text that search engines use to "learn" what each picture is about.

Description.
Web pages generally contain a summary that some search engines still show under the title in the search results. Most search engines, however, no longer show the description nor give it any more weight than body text.