The first implementation of CSS was drawn up in 1996, was released in 1999, and has been supported by all browser releases since 2001. The standard for this version, CSS1, was revised in 2008. Beginning in 1998, developers began drawing up the second specification, CSS2; its standard was completed in 2007 and revised in 2009.
Development for the CSS3 specification commenced in 2001, with some features being proposed as recently as 2009. Therefore, the development process will likely continue for some time before a final recommendation for CSS3 is approved. And even though CSS3 isn’t yet complete, people are already beginning to put forward suggestions for CSS4.
In the previous chapter, I detailed the various CSS attribute selectors, which I will now quickly recap. Selectors are used in CSS to match HTML elements, and there are 10 different types, as detailed in Table 19-1.