Ever noticed anything a little different about the drop-down menus on Amazon's website? Ben Kamens has, and he's published an illuminating explanation on his website. According to Kamens, lead developer at Khan Academy, the distinguishing factor is Amazon's speed — moving your cursor along the site's main drop-down brings up submenus almost instantly. That kind of responsiveness is rather unique in web design, and, as Kamens explains, it's something Amazon achieved thanks to a subtle, yet clever algorithm.