A well-categorized site map not only makes customer navigation easier, it also assists the Search Engine spiders crawl all the major pages of your Yahoo! Store helping them index your site better. This enhancement will replace that with a text-based description of the item image that can be crawled by the Search Engine spiders helping them index your site better. These tags also get displayed when visitors hover over the item image while browsing making your site more optimal. This tag also helps when the image can not be loaded for some reason, so visitors have an idea what that empty space is about. It's good to do everything you can to help Search Engines direct customers to you!