They did a lot of usability testing on the first iteration as well. They didn't test it in the market, since it didn't exist in a product yet, but they tested i

They did a lot of usability testing on the first iteration as well. They didn't test it in the market, since it didn't exist in a product yet, but they tested it. Jensen Harris [−π] has a large number of blog posts on the development and design history of that particular UI and a lot of information on why they have done things a certain way. [−π]: https://blogs.msdn.microsoft.com/jensenh/2008/03/13/table-of-contents/ https://blogs.msdn.microsoft.com/jensenh/2008/03/13/table-of...