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Look your best, even to those who can't see straight.
After reading that last section, you may well have thought "Hang on; not everybody has the latest and greatest browser." True enough; for example, as of February, 2010, there was still a distressing one in ten people saddled with Internet Explorer 6. Though analysis of your current Web server logs may indicate that your numbers are higher or (hopefully) lower, taking the present bête noire of the Web industry into account fits with our opening declaration of "Best viewed with any browser." "Internet Exploder 6", as it is widely known, either does not implement or incorrectly implements many, many features specified in the relevant standards (which are complied with by the majority of other browsers, progressively including later versions of IE).
There are two complementary approaches taken by Web developers to deal with differences between the browsers used to view a site.
Progressive enhancement takes the conceptual approach of
The aim is therefore to guarantee a certain minimum standard for presentation – akin to what would be seen by a search engine's Web crawler or a text-only browser such as Links.
In contrast, graceful degradation starts with the richest, most full-featured presentation, and then selectively disables or chooses alternates for features not supported by the visitor's browser.
While the practice of graceful degradation initially became widespread before the growth of progressive enhancement, it is now losing favor among clients and developers. If progressive enhancement fails to enable a feature for a particular viewer, the page is still usable. However, if graceful degradation fails to disable an unusable feature, the page may not be usable at all – or, in severe cases, a defect in the browser may cause it to crash entirely.