"A printed encyclopaedia is obsolete the minute that you print it, " Mr Cauz said.

BBC: Encyclopaedia Britannica ends its famous print edition

"We're a victim of our own success, " said Jorge Cauz, senior vice president for sales and marketing of Britannica.com Inc.

CNN: Free, but not easy -- encyclopedia's Web site jammed

After the initial rush tied up the site, it functioned normally overnight but became clogged again early today as Americans woke up and sat down at their computers, Cauz said.

CNN: Free, but not easy -- encyclopedia's Web site jammed