There are a few clear reasons. The medium itself is a big factor, but the tools and the workmen are also to blame. As some people point out - quite rightly - the Web is not print, it is an entirely new medium. And as with every new medium that appears, the old rules, the old ways of doing things, have to be reassessed. Ink on vellum required dramatically different approaches and techniques to chisel on stone, as did wood and then metal type on paper. Interactive, screen-based publishing is a massive change, on a par with Gutenberg’s invention of the printing press with movable type.
But this doesn’t mean that we have to throw out absolutely every rule which applies to print design simply because the medium has changed. We may not be dealing with paper, but we’re still juggling information in the form of words in visual layouts. What we have to do is distinguish between the rules which apply to typography in general, and the rules which apply to just a particular medium.
Of course sorting out the ‘best practise’ rules and guidelines to the satisfaction of both creative designers and technical gurus is quite a challenge. Few people can manage to stand in both camps, tending instead to polarise towards one set of opinions or the other. Mainstream designers may attempt site designs that are technically impractical, while code-writers are more inclined to produce technically functional but visually dysfunctional sites. This isn’t always the case, but everyone concerned with Web design should take a professional attitude to both design aesthetics and technical production.
One of the main design goals for both print and Web delivery is legibility. The precise methods for achieving this aim in each medium may be different, but the goal is the same. There are many cases where traditional rules of thumb aren’t exactly right, but aren’t exactly wrong either. Site designers mustn’t try to reproduce print-oriented approaches too literally on the screen, but equally they mustn’t dismiss design input as mere decoration which can be put off until the end of a project.