#66595 by AjK: add a default title to the search box, which can be altered/styled out if needed

modules/search/search.module

@@ -1072,6 +1072,7 @@ function search_form_submit($form, &$form_state) {
 function search_box(&$form_state, $form_id) {
   // Use search_keys instead of keys to avoid ID conflicts with the search block.
   $form[$form_id .'_keys'] = array(
+    '#title' => t('Search this site'),
     '#type' => 'textfield',
     '#size' => 15,
     '#default_value' => '',