A box with a blue outline appeared in my bookmark drop-down menu. I can't get rid of it, and it obstructs the view of the bookmarks as I scroll up or down. Help!

I was trying to bookmark a page, using the "Choose" menu in the bookmarks. I must have touched a key by accident, and a box with a blue outline & the name of one of my folders appeared in my bookmark drop-down menu. At first the box contained the folder name, then I was trying to delete the box, and erase the name, thinking it might get rid of the box, but it didn't. I can't get rid of this box! It obstructs the view of what is underneath. It stays in the same position as I scroll up & down in the drop-down menu, and it hides what is underneath. Please help me get rid of this box. It is driving me crazy! Thanks!