Fixing a broken link.

views/about.html.erb

@@ -50,7 +50,7 @@
        <a href="http://www.markboulton.co.uk/journal/comments/five-simple-steps-to-designing-grid-systems-part-3">3</a>,
        <a href="http://www.markboulton.co.uk/journal/comments/five-simple-steps-to-designing-grid-systems-part-4">4</a>,
        <a href="http://www.markboulton.co.uk/journal/comments/five-simple-steps-to-designing-grid-systems-part-5">5</a>)
-      on grid design. He's also working on a <a href="">book</a>.
+      on grid design. He's also working on a <a href="http://designinggridsystems.co.uk/">book</a>.
     </li>
     <li>
       <a href="http://www.miketownson.com/">Mike Townson</a> &mdash; for reporting a <a href="http://timkadlec.com/2013/01/windows-phone-8-and-device-width/">bug</a> related to Windows Phone IE and desktop IE10 "snap mode."