If your hosting server is not fast enough, you may want to replace your self-hosted jquery with Google CDN-hosted jquery. You may think that you are not using that script, but most of your plugins do.

WordPress scripts are registered on a script queue using tags. So, WordPress won’t load the same javascript library twice. If you want to change the default WordPress jQuery to google jQuery, just put the snippet below to your functions.php file.

add_action('init', 'wpassist_register_theme_scripts');
function wpassist_register_theme_scripts(){ 
  if(! is_admin()) { 
    wp_deregister_script( 'jquery' ); 
    wp_register_script( 'jquery', 'http://ajax.googleapis.com/ajax/libs/jquery/1.8.0/jquery.min.js' ); 
    wp_enqueue_script( 'jquery' );
    wp_enqueue_script( 'theme-script', get_stylesheet_directory_uri() . '/scripts-directory/theme-script.js', array('jquery') ); 

This code will tell WordPress to load google jQuery when a plugin needs that.