Type on the web is in its early stages of development. I predict that it will change radically, and a new set of guidelines on how to lay out type for web will emerge.
Already one difference is that the usage of serif and sans serif fonts seems to switch from the use in print. Previously, serif fonts were commonly used for body text to improve legibility, whereas sans serif fonts could provide strong, bold headers. On the web, technology has defined what is best. Sans serif fonts have become the accepted norm for body text. Because a screen is composed of pixels, it is not practical to have serif fonts in varying sizes for body copy- but they can add the critical contrast in headers.
So for usability purposes, sans serif fonts are the norm for body copy. But even that is constrained. There is a safe list of fonts, normally covering Arial, Times New Roman, Georgia, Verdana, Tahoma and Trebuchet MS- any other font choice and you risk making the site visually unappealing to the viewer as they may not have the font installed. Some websites, including nike.com, have adopted images on their headers/tabs so that they can use the type they wish.
Unlike print, screens operate the additive colour system (shown). It may not be a good idea to display lots of type on white backgrounds as instead of providing strong contrast, it can stun the viewer with glare and give them eyeache.
Type on the web has a long road of development ahead of it, but it seems to be increasingly the case that the type used is defined by the technological constraints rather than the wishes of the designer. Perhaps a good thing?
