Yahoo! free up my form
If you use 'Tab' to quickly move between form fields then I'd say that its now muscle-memory to 'type username. press tab. type password. press enter'. Well yahoo manages to break it, by introducing a linked email id, right between them. which means i end up typing my password twice. Its 2008 people! If you don't know what to type in the username box, you shouldn't be using it.