In October 2002, Yahoo made a significant change in how it presented search results. In the past, the main editorial listings shown on its page had come from its own human-compiled directory (which is described more on the Yahoo Directory page). Now, the main editorial listings at Yahoo come from Google crawler-based editorial results.
These Google listings at Yahoo appear under the "Web Matches" heading and make up the bulk of information shown on the Yahoo search results page -- and thus are one of the major ways people may find your web site via Yahoo.
In short, do well with Google and you'll also receive good traffic from Yahoo. Do learn about ranking well with Google's editorial results, see the How Google Works page. The remainder of this page explains in more detail exactly how Yahoo makes use of Google's information.
If you compare the same searches at Yahoo and Google, you will see differences, which could lead you to believe at first glance that Google results are not being used. However, most of the differences are due to Yahoo "enhanced" Google's results based on information from its own directory.
Let's see an example of how this works. Here's are the top two search results for "hiking boots" at Google:
Now here are the top two for the same search at Yahoo:
If Yahoo's Web Matches listings are taken from Google's editorial results, then why does the first listing in these examples seem so different?
In Google's results, Google has created the title and the first line of the description for the MerrellBoot.com page by automatically from content on the web page itself. The Page Descriptions section of the How Google Works page explains this more. In addition, because the page is listed in Google's version of the Open Directory, it also shows a separate "Description" line and a "Category" for the page. This also explained more in the Page Descriptions section of the How Google Works page.
In Yahoo's listings, Yahoo automatically reviews the pages that Google sends it and checks to see if they are listed in the Yahoo Directory. This is true for the first page listed. Because of this, Yahoo replaces the Google title and description for the page with its own human-edited title and description. This can make it seem as if Google and Yahoo are showing different results, but if you look closely, you'll see that the URL of the first page is the same in both places -- www.merrellboot.com.
In addition, any page that Yahoo recognizes as being in its own directory gets a "More sites about" link that appears below the page description. A red arrow also calls attention to this link. Clicking on the link takes you to where the page "lives" within the Yahoo Directory, where you can also see other pages considered similar to it by Yahoo's editors. Additionally, special icons may appear if your site has been deemed cool or a top pick in the Yahoo Directory. The Sunglasses section of the Yahoo Directory page explains this in more detail.
Now look at the second listing from Google. You can see that the title and the first part of the description for that listing are used exactly by Yahoo. In addition, you can also see there is no "More sites about" link for the second listing at Yahoo. This is because the page is NOT listed in the Yahoo Directory, so Yahoo cannot enhance the listing with its own information.
Differences Due To Clustering
Another reason why you may see differences between the listings at Google versus Yahoo is because Yahoo does tighter "clustering" than Google. At Google, up to two web pages from the same web site may be displayed on the results page. At Yahoo, only one page from the same web site will be shown. In other words, none of Google's "indented" listings will appear at Yahoo. See the Clustering section of How Google Works for more about how clustering operates at Google.
Differences Due To Ranking Algorithms
In most cases tested just after Yahoo switched to using Google results, any major differences between listings in both places were usually explained by Yahoo enhancements being added and clustering. After that, there were a few cases where the exact order of some web pages might be slightly off.
For example, a test query for "halloween" at Google ranked a page for Halloween Magazine in position 5 and HalloweenMovies.com in position 6. At Yahoo, these were swapped. HalloweenMovies was in position 5, while Halloween Magazine was in position 6.
Why was this swap made? There's no clear reason, unfortunately. Both pages were listed in Yahoo, so their titles and descriptions were enhanced. For the page that moved up, it did use the word "halloween" in both its title and description. So, this could be one factor that Yahoo is using to slightly reorder Google's results. However, there were many other sites above it that had the search term only in their titles, so it is not an overriding factor.
Yahoo itself provided two examples that showed dramatic differences between the order of its results and Google's: "pizza" and "mexico," and I came across a third in my own testing: "las vegas." Either the pages shown, the ordering of those pages or both are radically different between the two. Unfortunately, Yahoo provides no explanation about why this is happening, nor is there any pattern so far detectible.
One thing that may be happening is that Yahoo measures what people click on in its search results. This clickthrough measurements might be used to further refine the results -- and it could be that only a few queries are showing the results of this refinement because they may have been selected to exposure for beta testing before Yahoo unveiled its new results to the public. If so -- or if other factors are involved, then we may see the listings at Yahoo begin to diverge from Google's over time.
Another major change that could happen is that Yahoo may bring results from other search engines into its results at any time, as explained more in the article below:
Yahoo Renews With Google, Changes Results
The Search Engine Update, Oct. 9, 2002
Such a move could easily produce more dramatic differences between the results at Yahoo and Google. The article below explores more about Yahoo's intentions about using multiple search providers.
Yahoo Sponsor Matches