1
That's the line that automatically placed over footnotes to separate them from the main body of the document.
Assuming Word 2013:
0
If Techie007's answer doesn't work...
Try this:
I experienced a similar issue in the Outlook 2007 editor (Word!) just yesterday.
2Note: I can see at least TWO lines (black), which one is it that you have a problem with? – Hannu – 2015-09-11T17:15:22.777