update

Author: sveinlin

doc/.src/book/preface.do.txt

@@ -261,7 +261,7 @@ stated, even if it was already met in another chapter.
 
 All program and data files referred to in this book are available
 from the book's primary web site:
-URL: http://hplgit.github.io/fdm-book/doc/web/.
+URL: https://github.com/hplgit/fdm-book/.
 
 === Acknowledgments ===