To put it bluntly, he thinks most interfaces for desktop software and Web sites are pretty poor. A great deal of information is packed into the front page of the site, offering a thorough knowledge of what lies on pages one level below. Yet careful arrangement of font sizes, and ample use of white space on the site keep the feeling open and uncluttered.
Colors are simple and few.
Contrasts between background colors and text colors are stark. The page makes few demands on the user's technology. Nielson does have some reservations, though. That last point is perhaps the most salient of all. The discipline to recognize what users actually do on your site, and to avoid the blinders of your own expectations of what they'll do, is hard-won.