Margins can be specified as a percentage of the width of the element which contains them. As browser windows widen and narrow, the layout of an element adapts to maintain the same proportions, and so the whole page layout adapts. Margins, text indentation and other layout aspects can also be specified in relation to the size of the text they contain. This is another way to make page designs adapt to a reader's settings. Colors The web is by and large a more colorful medium than the printed page.
Color is cheaper on the web.
But color poses difficulties to adaptability as well. That is, regardless of any other ability, because warning information is almost invariably conveyed using red for danger and green for safety. It's a shame that warning lights aren't simply adaptable. It would be a shame as in the near future most web browsers will provide simple ways for readers to adjust the color of elements on a web page, via user style sheets, which can override your style sheets. And avoid relying on color combinations to alone convey meaning.