There are occasions when you’d want to create a heading in the SharePoint Quick Launch navigation without your heading being navigable. In the past, I believe it was possible to create a heading without specifying a URL, but in SharePoint 2013, the URL field is mandatory—at least from the Site Settings interface. (See below for update.)
Option 1: enter “#” as the URL from Site Settings > Look and Feel > Quick Launch
Option 2: Use the “EDIT LINKS” option under the Quick Launch and leave the URL field empty. Although, the URL field is mandatory from Site Settings, you can leave it blank from this interface.
Both of these options create a link to the site’s home page, but they allow you to create a heading without using an absolute URL to some random page.
Update: Option 3:
There is actually a way to do it the old fashioned way; it’s just not that intuitive if you happen to try the UI for editing the Quick Launch above. Go to Site Settings > Navigation and then scroll down to the Structural Navigation: Editing and Sorting section.