Sometimes I find google's UI design is a little lacking in intuitiveness. If you want to remove a Web site from your analytics account, go to this page for the details.
It turns out that you can't set up more than 25 sites in your google Analytics account. You can view more sites than that, but any additional sites have to belong to another account. According to their support people, this is a performance issue and they are working on it.
This issue limitation may have been removed now May 2014.