Yahoo Inc. said it is planning to shut down several "underperforming" and "non-core" Web properties, including the venerable search site AltaVista, as it continues a years-long turnaround effort.

Sites that could be affected by the moves include Delicious, a so-called social bookmarking service, search site AlltheWeb, and online news aggregator Buzz, according to an internal company slide that was posted on the Web on Thursday.

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