If you were inclined to rearrange the order of Menu items for whatever reason, this can easily be done by going to the Admin Menu.
Hover over Structure>Menus> and click on Main Menu, or perhaps the Footer Menu if you have one.
You will now see a page similar to the one below, where you will find take the handle on the left hand side and drag up or down depending where you would like the menu to be reordered.
When finished, click save.