If you are using server-side caching in Drupal. That is if you have the following setting enabled in "Administer -> Site Configuration -> Performance"...

Then you when are making changes to your site, you may not see the updates in your live site right away. During development or when making setting changes such as changing the order of your menu, you can disable those above cache settings and then clear the cache.

If you had made changes to your site and they are not being reflected in your live site, try manually clearing the server-side cache.

To clear the server-side cache in Drupal.

1. Log into Drupal admin
2. Click Administer -> Site Configuration -> Performance
3. Scroll to the bottom and click the button "Clear cached data"

In addition to clearing the Drupal server-side cache, you may also need to clear your browser cache by pressing Ctrl F5 on your browser.