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.