Cacher is the code snippet organizer for pro developers

// create search filter
function xmit_search_filter($query) {
if ( !$query->is_admin && $query->is_search) {
$query->set('post__not_in', array(203,138,291) ); // id of page or post
// $query->set('cat','-5,-24'); use this to exclude categories
}
return $query;
}
add_filter( 'pre_get_posts', 'xmit_search_filter' );