to paraphrase a certain politician.
Above all else a web site is a means of communication, and the easier it is for the visitor to get the message the more likely he/she is to buy the product or service, or support the charity, or whatever.
To my mind the best sites are those without animated gifs, fancy backgrounds, music, twenty different fonts and ten different colours. A site should look clean and attractive, and be simple to navigate - three clicks from the homepage to the bottom of the site for the average site (although large corporate sites can be forgiven for having a deeper structure).
External links should work, and link to the external site's homepage, no others. There should be well-written text in small bite sized chunks - no massive 1000 word screeds. Research shows that people lose interest in big text blocks, they move on.
Plenty of well-prepared images don't go amiss - properly sized in the image editing program (not dragged to size in the WYSIWYG design application).
No bad language, or bad-taste jokes.
No hit counters or visitors books.
Bah, humbug! I'm off to pull the wings off some flies.