When users receive a book result during an A9 search, they can click on the page number to view a specific page, provided they are registered Amazon.com users. A results page also includes the date and time when the user last clicked on the link and provides site information from Amazon's Alexa service. It will also link to cached Google data. In the first release, output was limited to 10 results per page. Customization features include the ability to alter the width of the three different columns on each page—Web searches, book searches, or history—and have future searches reflect the changes.

Searchers can call up their search histories from A9.com storage and click on a link to re-execute the search or edit the history, e.g., deleting an entry. If they wish, they can hide the history window and require a password to reopen it. The centralization of the search history on A9.com's computers—as opposed to cookies on users' computers—means that the tracking of sites visited and search histories will work from different computers. Searchers who use their Amazon login will see searches done on the Amazon.com site also merged with A9 searches. Folders hold different categories of search history, e.g., recent searches, searches 2 weeks ago, etc.

The A9 Toolbar expands search options beyond the A9 system to include searches on the Internet Movie Database (an Amazon property), the Merriam-Webster Online Dictionary and Thesaurus, along with full searching on the "parent" sites, i.e., Amazon.com and Google. At this point, the A9 service does not encompass Google's entire database.

When using the toolbar, searchers will see their search terms highlighted in light yellow. A highlighter menu allows searchers to jump to each occurrence. If, upon perusing results, searchers decide other terms have more interest, they can enter them into the search box and click on the highlight button to change the target of the highlighting. A diary feature lets users attach notes to a Web page and refer to them whenever they revisit that page from any computer used. A9's toolbar automatically saves notes whenever users either cease typing or switch to a new page. Toolbar users can also build their own directories of Web sites by reviewing all diary entries to get the full list of entries on a Web page and then use an HTML editor to build separate Web pages for different sets of annotated Web site listings.

Site information provides related links, site statistics such as traffic rank, sites linking to this site, and user ranking. Users can even review sites for posting on Amazon.com. Finally, the toolbar offers a pop-up ad blocker. The toolbar works on computers running a Microsoft Windows operating system, Internet Explorer 5.5 or later, and with an Amazon.com account.

With all the customization and centralization of user search records in A9, some concerns have been expressed about privacy issues. A9 posts an extensive privacy policy statement with many examples of how its policies work, but it also offers a separate alternative. Users interested in doing A9 searches, who do not want the system to track them or their searches, should go to http://generic.a9.com. This site will not recognize A9.com or Amazon.com cookies. A9 warns that this means users will not receive the personalized services. A9 also automatically installs a "family filter" to block pornography and other offensive material. At launch, there was no way to turn the filter off.

Google and Amazon have partnered since April 2003. Google expands its outreach by partnering with over 130 companies at this time. A9 has another project in the works, improving the eCommerce search engine that Amazon and some of its partners use. By the way, the name A9 comes from Amazon's chief algorithms officer, Udi Manber, who moved to Amazon from his position as chief scientist at Yahoo!. The A9 conveys the number of letters in the word "algorithm."

Most of the reviewers of the new site have praised it for its appeal to end-user searchers, but pointed out that, at this point, it would have limited appeal to power searchers. On the other hand, it might have some appeal to intermediary searchers working with clients and doing extensive Web searching. Since A9 holds search histories centrally and allows toolbar users to annotate result lists, one could envision professional searchers using the service as a collaborative tool. Use A9 for searching and annotating search results. Share the registration password with clients or colleagues working in a collaborative mode. That circle of associates can search and annotate their own results, or just expand the annotations on entries provided by others. Of course, one would recommend that the user identification tying all this together not be connected to anyone's credit card, as it might if based on an Amazon.com registration. However, it should be simple to set up an e-mail identity. In fact, if one used Google's new Gmail, one could add a gigabyte of storage to the project's resources.

And all for free. God bless the Web.