xxii Introduction
Since publication of the first edition of this book, we’ve seen four major
versions of Safari and three of Internet Explorer. Firefox has become an
auto-updating “evergreen” browser, Chrome has switched from the Web-
Kit engine to its own Blink, and Opera has discontinued work on its own
Presto engine to also use Blink.
In addition, the rise of preprocessors such as Sass and LESS has brought
the power of programming languages into our stylesheets and dramatically
changed the way we write CSS. Most professional developers now use a pre-
processor as a core component of the website authoring tool set.
Many CSS specifications have changed since the first edition, too. Some
have been discontinued, and many more have been created. And the CSS3
of 2010 had many more cross-browser implementation differences, but the
differences are much fewer today as browser vendors have placed more
importance on adhering to standards.
In other words, this second edition is not simply a light edit of the first;
every chapter has been fully revised to reflect changes to the specification
and to remove outdated implementation information and experimental
properties not in the specification. Certain chapters (those on media que-
ries, Flexbox, grids, and the future of CSS in particular) are almost entirely
new, and I’ve added new chapters on values and sizing as well as blend modes,
filter effects, and masking.
Here’s to the next four years of change.