How to add site Validation for all pages
One way to do that is using the "site_verify" module and you can add another hook to add it to all page that will look like this:
 /**
 * Implements hook_init().
 *
 */
function YOUR_MODULE_init() {
  $meta_tags = db_query("SELECT svid, meta FROM {site_verify} WHERE meta &lt;&gt; ''")-&gt;fetchAllKeyed();
  foreach ($meta_tags as $svid =&gt; $meta_tag) {
    $data = array(
      '#type' =&gt; 'markup',
      '#markup' =&gt; $meta_tag . "\n",
    );
    drupal_add_html_head($data, 'site_verify:' . $svid);
  }
}


you need to change "YOUR_MODULE" with your custom module name. Also clear drupal cach after adding it