Avoid "Click here for an HTML tutorial"
Use instead "See the NC State Computing Services' HTML tutorial"Contextual links make your document more usable as printed material.
See my really cool image page!
See my really cool image page [2800K]!
White space is even more important online than for paper documents; use paragraph tags and lists to break up online text. Source documents must also be easy to edit so use blank lines (they don't show up after all).
Use images that clarify or illustrate, while avoiding "image for image sake." Also consider client and server speed: an excessively long download time can be very annoying, especially if you wait 2 minutes only to find that someone decided to use their entire icon collection on one page.
There are almost always differences in how headings and preformatted text (for example) appear in different browsers and even different versions of the same browser. Test your pages on all the browsers if you can!
Give the date of the last modification and the name of who's in charge of the document on at least the first page. Also, since date representation is so varied around the world, use the name of the month.(Last modified on 4/4/95 by rmn) could be August 4 or April 4.
(Last modified on August 4, 1995 by rmn) is preferred.
This is a tough one. Should your document be formatted to print easily? Doing so would entail long, scrolling documents which are sometimes difficult to navigate online. And, if you want the document to be printed, why is it online in the first place? You probably need to evaluate what "need" your page is serving. If it might be beneficial to print for some folks, you should probably keep that in mind as you design your document.