Web browsers are funny things. On the one hand, they’re supposed to be lightweight little programs that just let you view websites, and on the other, they carry the same burdens as operating systems and application suites, trying to provide everything to everyone. Here in this little essay I explain what I know about designing browsers. I’m in the lucky minority of people that have actually designed successful browsers, or parts of them, for any length of time, and with Firefox and Opera in the headlines, and the art of browser design becomes important again, I thought I’d write down some of what I know. Its been years since I was a program manager on the Internet Explorer project, but I’ve maintained interests in the design of navigation and searching systems of all kinds: what follows is a rough summary of what I’ve learned.