HTML and CSS Reference
THREE KEY PRINCIPLES OF
By this point, you're probably eager to get going with a
real HTML5 page. But first, it's worth climbing into the
minds of the people who built HTML5. Once you under-
stand the philosophy behind the language, the quirks,
complexities, and occasional headaches that you'll en-
counter in this topic will make a whole lot more sense.
1. Don't Break the Web
“Don't break the Web” means that a standard shouldn't
introduce changes that make other people's web pages
stop working. This rarely happens.