Microsoft Corp has unveiled its Home Advisor web site, designed to provide a single point of access to real estate databases, online searches and mortgage calculators built by other vendors. Though customers can’t close a deal online, the site has already annoyed rivals QuickenMortgage and ELoan, Yahoo’s real estate web site and the National Association of Realtors’ Realtor.com. The Wall Street Journal reports that today fewer than one per cent of mortgages begin online. The total market, however, is worth $1.2 trillion. As the Nando Times points out, that’s 15% of the nation’s gross domestic product. The web-initiated slice of the home buying pie seems certain to grow, and Microsoft wouldn’t be Microsoft if it didn’t try to optimize its own share. Even so, rivals shouldn’t lose any sleep just yet. Home Advisor is still full of bugs, throwing up JavaScript errors, broken images and empty links on virtually every page.