Index: modules/node/node.pages.inc
===================================================================
RCS file: /cvs/drupal/drupal/modules/node/node.pages.inc,v
retrieving revision 1.29
diff -u -r1.29 node.pages.inc
--- modules/node/node.pages.inc	17 Feb 2008 19:29:07 -0000	1.29
+++ modules/node/node.pages.inc	26 Mar 2008 22:10:45 -0000
@@ -399,6 +399,7 @@
       $output = theme('node_preview', $cloned_node);
     }
     drupal_set_title(t('Preview'));
+    drupal_add_js(drupal_get_path('module', 'node') .'/node.js');
 
     return $output;
   }
Index: modules/node/node.js
===================================================================
RCS file: modules/node/node.js
diff -N modules/node/node.js
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ modules/node/node.js	1 Jan 1970 00:00:00 -0000
@@ -0,0 +1,14 @@
+// $id$
+
+/**
+ * Make sure that users don't go to a different page and unintentionally 
+ * lose their content.
+ */
+Drupal.behaviors.nodePreviewProtect = function(context) {
+  $("div.preview a", context).click(function() {
+    if (!confirm(Drupal.t("Are you sure you want to navigate away from this page?"))) {
+      // Do not navigate away from the page.
+      return false;
+    }
+  });
+}