diff --git a/documentation/content/en/books/porters-handbook/makefiles/_index.adoc b/documentation/content/en/books/porters-handbook/makefiles/_index.adoc
--- a/documentation/content/en/books/porters-handbook/makefiles/_index.adoc
+++ b/documentation/content/en/books/porters-handbook/makefiles/_index.adoc
@@ -2611,6 +2611,9 @@
 If the same content can be accessed via HTTP and HTTPS, the URL starting with `https://` shall be used.
 If the URI is the root of the website or directory, it must be terminated with a slash.
 
+The ports framework may provide a default value for the WWW variable.
+Whenever the WWW variable is set in the [.filename]#Makefile# its value must be string literal and not include variables.
+
 This information used to be placed into the last line of the [.filename]#pkg-descr# file.
 It has been moved into the Makefile for easier maintenance and processing.
 Having a `WWW:` line at the end of the [.filename]#pkg-descr# file is deprecated.