Unintended white space on the main menu

I showed a client around the admin panel of their site, and within a day they had pasted a random URL somewhere (they don't remember where) while trying to add it to a menu. Now the main menu has an empty white space on one side. Looking at the compiled code, there is an unlinked URL in the space, invisible. Any ideas where it might be living so I can erase it?

Thanks!

Here's the site:
http://contemplativecentre.org/