--- a/css.rst	Fri Jan 27 22:57:53 2017 +0200
+++ b/css.rst	Sat Jan 28 14:37:19 2017 +0200
@@ -6,6 +6,23 @@
 .. contents::
    :local:
 
+CSS specification
+=================
+
+Starting from CSS level 2 specification splited into individual modules. Each
+module have own levels.
+
+CSS level 3 means CSS level 2 plus modules that refine and extend CSS 2.
+
+https://www.w3.org/TR/CSS/
+  Definition of CSS standards.
+https://www.w3.org/Style/CSS/
+  Home page for CSS specification umbrella.
+https://www.w3.org/Style/CSS/current-work
+  Status of all modules.
+https://www.w3.org/TR/CSS2/
+  CSS level 2 rev 1.
+
 Adding CSS to HTML
 ==================
 
@@ -79,8 +96,9 @@
 
 See:
 
- * http://www.w3.org/TR/CSS2/selector.html
- * http://www.w3.org/TR/css3-selectors/#selectors
+ * https://www.w3.org/TR/CSS2/selector.html
+ * https://www.w3.org/TR/css3-selectors/#selectors
+ * https://www.w3.org/TR/CSS/#selectors
 
 CSS include statement
 =====================
@@ -180,7 +198,7 @@
 
   * http://www.quirksmode.org/css/contents.html
   * http://en.wikipedia.org/wiki/Comparison_of_layout_engines_%28CSS%29
-  * http://www.css3.info/modules/selector-compat/
+  * https://www.css3.info/modules/selector-compat/
 
 Editor support
 ==============