add link to second edition

Author: keithjgrant

Diff for: README.md

@@ -1,6 +1,9 @@
 # CSS in Depth
+
 Code listings from [CSS In Depth](https://manning.com/books/css-in-depth) by Keith J. Grant
 
+_Note: These listings are for the first edition. For second edition listings, see [the second edition repository](https://github.com/cssindepth/css-in-depth-2)._
+
 At first glance, it may appear that some listings are missing—Because working examples requires both HTML and CSS, I have put most listings in an HTML file, using <style> tags for the CSS. This means that both an HTML listing and CSS listing are combined in one file in the repository.
 
-For example, in Chapter 1, listing 1.1 is HTML code and listing 1.2 is CSS that is meant to be applied to that HTML. I have included these both in the repository in the file named ch01/listing-1.2.html.  Changes are made to this CSS in ch01/listing 1.3; these are included in ch01/listing-1.3.html, along with the corresponding HTML from listing 1.1.
+For example, in Chapter 1, listing 1.1 is HTML code and listing 1.2 is CSS that is meant to be applied to that HTML. I have included these both in the repository in the file named ch01/listing-1.2.html. Changes are made to this CSS in ch01/listing 1.3; these are included in ch01/listing-1.3.html, along with the corresponding HTML from listing 1.1.