Comment by blahblah7777

Yahoo’s implementation of this (Sign In Seals) works with a Flash (LSO) Cookie. So, they remember your username (and your personalized picture / seal) by inspecting the Flash cookie. I remember the first time I tried it—and being impressed—but then wondering how the fuck they did it. Then being less impressed when I realized that it doesn’t work after clearing your Flash cookies (or if you have Flash turned off).