That is because yahoo has its own servers and yahoo.com is the only website at that IP. For mere mortals like me with a dreamhost account or something, there's

That is because yahoo has its own servers and yahoo.com is the only website at that IP. For mere mortals like me with a dreamhost account or something, there's probably dozens of sites on the same IP, so your computer has to first connect to the IP then send the HTTP "Host:" header to say what site it wants.