PROVIDE A FALLBACK FOR OUTDATED WEB BROWSERS

Pre-HTML5 web browsers will react differently to your new HTML5 code. Previous HTML specifications state that if a browser encounters a tag it does not understand, it should ignore that tag but continue processing the tag’s contents. Unfortunately, this specification was implemented differently by the browser vendors.

When an HTML5 tag is viewed by a browser, regardless of its version, one of three things will happen: 1.) The tag is recognized as an HTML5 tag. It is fully customizable by CSS. 2.) The tag is considered an error, but a DOM node is still created. The tag is still customizable by CSS, but a display: inline style is implicitly applied. Or 3.) The tag is considered an error and ignored. ...

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