Documenting the deprecated.js script.

lib/deprecated.js

@@ -23,6 +23,20 @@
  * @requires OpenLayers/Geometry.js
  */
 
+/**
+ * About: Deprecated
+ * The deprecated.js script includes all methods, properties, and constructors
+ * that are not supported as part of the long-term API.  If you use any of
+ * these, you have to explicitly include this script in your application.
+ *
+ * For example:
+ * (code)
+ *     <script src="deprecated.js" type="text/javascript"></script>
+ * (end)
+ *
+ * You are strongly encouraged to avoid using deprecated functionality.  The
+ * documentation here should point you to the supported alternatives.
+ */
 
 /**
  * Namespace: OpenLayers.Class