Obviously, John Walker has an interest in space and science. His Fourmilab Switzerland website is full of links to astronomical goodies. The website is easy to navigate with a home button on the upper left (the Fourmilab logo) and four quick buttons on the top right. A large list on the left is divided into categories and provides links directly to specific subjects. When clicked, these appear in the main section. Clicking on items in the main panel will bring up a full page item. Use your 'back' key to return to the menu page. The Astronomy and Space page lists a variety of programs and interactive items as well as documents and images provided by the author. Most of the applications and screen savers are written for Microsoft Windows 95/98/Me and NT/2000/XP. Some work in Windows 7 as well. There are a couple of Unix applications also. All material on the website is in the public domain other than a few clearly marked items.