According to the W3C, the logo is "a general-purpose visual identity for a broad set of open web technologies, including HTML5, CSS, SVG, WOFF, and others." ...

The Web standards group clarifies that its HTML5 logo really is just for HTML5. To tout your site's use of WOFF, SVG, and CSS, there are smaller, gray icons.

Below is the CSS3 logo that has been used until now. This time, the CSS-Next Community Group, the developer of CSS, has selected a new logo mark for CSS4, which will follow CSS3, and CSS5 and beyond.

Yes, we'll still be supporting IE 7 and IE 8 for some time, and yes, IE9 still lacks a few things, like support for CSS 3 text-shadows or HTML5's form elements, but it's a step in the right direction.