How is CSS different from HTML?

[SwatiSood]

CSS is independent of HTML and can be used with any XML-based markup language. The separation of HTML from CSS makes it easier to maintain sites, share style sheets across pages, and tailor pages to different environments. This is referred to as the separation of structure (or: content) from presentation.

[lisajohn]

HTML provides tags which are surrounding the content of any web page elements, whereas CSS consists of selectors which are surrounded by a declaration block. CSS has fragmentation, but HTML doesn't produce any such problems. CSS uses a much lesser code and thus produce much lesser web page loading time than HTML.