There's nothing our brains like so much as order and meaning. It's what they search for from the moment they encounter anything new - and that includes your web page. If brains can't find the sense and order they need, they soon grow exasperated and give up.
The best designers know this. They've also learned that, the more elaborate the design, the greater the risk of confusion. That's why they usually steer clear of fussy and showy designs.
Instead, their layouts have a 'quieter' feel, with all the individual elements directed at letting the page information unfold as easily as possible. Headlines, subheads, body copy point size, pictures, colours - all are used to 'signpost' the route the good designer wants the reader to take through the material placed before him. A route that's guaranteed to leave him feeling better informed, and better served, at journey's end.
In our culture, we're trained from the moment we start reading to scan from left to right, starting from the top left of the page and working down to bottom right. We develop a natural rhythm as we do it, with our eyes moving swiftly to the end of each line, then skipping back to the start of the next.
So far, so obvious. But it's the obvious that's often overlooked, particularly by designers who want to 'create an impression' by doing something radical, such as running the main headline around the page margin, or by making interesting shapes with the body copy.
I could go on, of course. I could talk about startling use of contrasting colours. Or reversing out large chunks of text. Or running it over a picture. Or experimenting with lots of different typefaces and point sizes. Or dotting illustrations all over the page.
All these stylistic touches may look really cool. And result in something you'd love to hang on your wall. But that's not the goal, is it? Your aim is to make life easier for your reader. Yet, too often, the kind of visual tricks listed here do exactly the reverse. They disrupt natural eye movement. They strain the eyes by asking them to jump around the page, from element to element, with the need for lots of re-focusing along the way. They frustrate the brain in its instinctive quest for logical order and meaning.
If you only want one guideline, make this it. Because, frankly, for all the reasons already given, there really is nothing more irritating to readers than design for design's sake.
This isn't to say your web page shouldn't use all the design elements and special touches that create style, pace, flair, excitement, intrigue, emotion. Of course it should! But these elements must always be relevant and appropriate, and not distract from a clear, coherent whole effect.
Remember this, and you'll vastly increase your chances of creating effective online design - a design that draws attention to the message, not to itself - a design that will serve your web site visitors rather than dazzle them.
-Phil Brisk (http://www.webdesignfromscratch.com/dont_decorate_communicate.cfm)