The class and id attributes allow page authors to create their own semantics on top of those that are part of the spec.
Because they possessed large beaks capable of cracking the larger, harder seeds that were available. In the absence of a drought, the larger finches possessed no distinct advantage over their smaller relatives, but when the environment changed, they were perfectly positioned to take advantage of the situation and not only survived the drought, but passed their genes along to the next generation of finches which, as you’d expect, tended to be larger. a. S. Beagle, by John Gould. HTML and CSS have a lot in common with the Galapagos finches.
The various elements and attributes used on a page provide additional meaning and context to the written words. They indicate important notions such as emphasis and provide supplementary information, such as the source of a quote or the meaning of an unfamiliar phrase. The third level of experience is the audio-visual one, expressed through the use of CSS and the use of inline images, audio, and video. As with HTML, implementations of CSS within a browser are necessarily fault tolerant, so browsers ignore that which they don’t understand; a fact that makes progressive enhancement in CSS a possibility.
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