Drupal 7 edd rel="nofollow" to menu links More about: https://api.drupal.org/api/drupal/includes%21menu.inc/function/theme_menu_link/7
<?php
// Add rel="nofollow" to menu.
function themename_menu_link__menu_name(&$vars) {
$element = $vars['element'];
$subs_menu = '';
// Add links for nofollow attribute add by menu link ID.
$include_id = array();
if ($element['#below']) {
$subs_menu = drupal_render($element['#below']);
}
if (in_array($element['#original_link']['mlid'], $include_id)) {
$element['#localized_options']['attributes']['rel'] = 'nofollow';
}
else {
$element['#localized_options']['attributes']['rel'] = '';
}
$output = l($element['#title'], $element['#href'], $element['#localized_options']);
return '<li' . drupal_attributes($element['#attributes']) . '>' . $output . $subs_menu . "</li>\n";
}
?>