Index: captcha.install
===================================================================
--- captcha.install	(revision 30487)
+++ captcha.install	(working copy)
@@ -112,8 +112,12 @@
   }
 
   // what to do after install?
-  drupal_set_message($t('You can now <a href="!captcha_admin">configure the CAPTCHA module</a> for your site.',
-    array('!captcha_admin' => url('admin/user/captcha'))), 'status');
+  $message = $t('You can now <a href="!captcha_admin">configure the CAPTCHA module</a> for your site.',
+    array('!captcha_admin' => url('admin/user/captcha')));
+  if (variable_get('cache', 0) > 0) {
+    $message .= ' ' . $t('Note that pages containing a CAPTCHA challenge will not be cached even though <a href="!performance_admin">page caching is turned on</a>.', array('!performance_admin' => url('admin/settings/performance')));
+  }
+  drupal_set_message($message, 'status');
 }
 
 /**