Often people place menu items manually because it's easier to find the menu link and fiddle with it than it is to find the pages and change the configuration within the page view. This is a big mistake. The menu manager should only be used to manage links outside the site and to non-standard content. If the content in the link is a page, you should stay in the page edit screen to edit its location and text for the link. This keeps the menu link tied to the menu item itself: the page. Disconnecting these virtually guarantees you'll have orphaned pages. That means you're going to create broken links.
Here's a simple example of such a mistake.

In this case, the website owner wants to place the page called Ring Size Help under the page called The Fifth "C." That's fine. But, he made a common beginner's error. He used the menu management screen to do it, and tried to link the page underneath the menu item he created. The system is nowhere near that complex. You need only do it in one place or the other.
Again, it's best to just leave the menus alone outside of the page edit screen.

You'll see here, he's already created a menu link called Ring Rize Help and is trying to link the page under that. What's wrong with that? This is the page, not a page under the page. It's not Ring Size Help and its sub-page Ring Size Help - it's just one page. So, the real parent isn't Ring Size Help, but the item you want that page under. In this case it's The Fifth "C" (as seen in the first screenshot above).
How do we correct this problem?
1st, delete the bogus link in the menu.

Then we go where he added the link.

See in this menu view, where you can tell that he added the Ring Size Help link and then added the link within the page edit view underneath this link.

There are multiple problems with this picture. For one, the website owner has created a web address (Path) called The Fifth C. That's not the path of any real page. The path is the address. For example, http://www.jasonn.com is an address and it's also a path. contact_me would be a path. contact_me would be that address plus a / plus the path when someone clicks on it. So, if your domain were domain.com, then contact_me in this space would be http://www.domain.com/contact_me.
We're just going to delete this entry because it serves no purpose.

He really wanted that link under The Fifth C where we saw his broken menu item. It's not nearly that complex. Just make the place you want directly above the page you are editing the Parent item and that's what happens.

The menu The Fifth C has a submenu item called Ring Size Help now. It shows up as a submenu item when you click on The Fifth C.
When you click on Ring Size Help it used to go to a broken link. But, now we've corrected that and made it a direct link tied to the page we just edited.

Now you can see clicking on this link works flawlessly. Most important, if the website owner changes the page, he can be assured that the system will update the menu link for him.
There's only one time it's appropriate to edit the menu directly.

When linking to an outside URL, like our website for example, you can add a link directly into your menus by pasting the URL and its complete path into the Path space. Otherwise, it's always best to edit the menu settings inside the page edit screens.
