Yahoo is quietly testing a search engine which users can customize by adding, removing and rearranging components, suggesting that the company may plan to make it easier for users to tailor search sites to reflect their interests.

Yahoo Alpha, which is hosted on an Australian domain, offers a default results page with a list of Web sites on the left hand column and six specialty search result boxes on the right hand column.

The specialty boxes display results from three Yahoo search engines: the Flickr photo service, the Answers question-and-answer service, and Yahoo News. It also returns non-Yahoo results from Google's YouTube video site and from the encyclopedia Wikipedia. Finally, it has a box for displaying search ads from Yahoo's online ad network.

It gives users the option to customize the default layout of the results page by repositioning the different elements and by adding or removing the specialty search boxes. Apparently, users can insert a search results page from any Web site that syndicates its content via RSS (Really Simple Syndication).

A quick test-drive of the site shows that anyone can query Alpha and obtain results in the default page, but to customize the layout and search sources, users need to log into Yahoo.

A handful of Yahoo Alpha sightings began sprouting up on the blogosphere on Wednesday. Asked for comment and details about Yahoo Alpha, which is in beta, or test, phase, the company would provide only the following statement on Thursday: "This is a very early prototype and we are always testing new products and services to get feedback from our users on improving the user experience."

Yahoo already provides a service called Search Builder to let Web publishers build customized search engines for their sites based on the Yahoo search platform. However, Yahoo Alpha seems targeted at end users interested in creating a search page tailored to their interests. Users can also share their Yahoo Alpha search pages with others.

As such, Yahoo Alpha seems to be yet another experiment in social search for the company, which has been exploring and providing search services that let users participate by contributing content and tags. For example, Yahoo Answers lets users answer each other's questions, while Del.icio.us lets users post and share their favorite Web site bookmarks. Flickr does a similar thing with photos.

Yahoo Alpha seems similar, at least conceptually, to Google's Co-op, which also lets users create a customized search engine. People can use their Co-op-created engine for their personal use, and they also have the option of embedding it on their Web site for others to use.

Social-search services have become popular as tools for users to tame the often unmanageable amount and breadth of search results that general Web engines return for average queries.