The Atomic Clock display is a service of the National Observatory.
If the clock shows up as a broken image, try reloading it.
The main atomic clock site is probably just busy. If reloading it doesn't help, you're possibly running into a browser incompatibility. Due to a limitation on the other end of the atomic clock set up, the only browsers 100% guaranteed to work are Netscape, Mozilla, and Firefox. We at Saugus.net regret this limitation, but it is beyond our control.
If the clock doesn't work with your browser, another option is the Official U.S. Time Clock; note that it requires Java in order to work properly.