diff --git a/free-programming-books.md b/free-programming-books.md
index f4692b7ed06ec2d5411f0451fe643cea6512f18b..65a78de774a4b07ee74c79fc6f1ddfdd9b44e6b2 100644
--- a/free-programming-books.md
+++ b/free-programming-books.md
@@ -23,7 +23,7 @@
 * [Go](#go)
 * [Grails](#grails)
 * [Haskell](#haskell)
-* [HTML / CSS](#HTML / CSS)
+* [HTML / CSS](#html--css)
 * [Java](#java)
 * [JavaScript](#javascript)
 * [JavaScript (Node.js specific)](#javascript-nodejs-specific)