A family of Microsoft word processing software products for creating web, email, and print documents.
If this is indeed a paragraph border, try the following: Add text below and above the line, and select all the text (at least three paragraphs). Display the Borders and Shading dialog box by clicking the arrow on the Border button in the Paragraph group on the Home tab. In the dialog box, click the "None" option. See also http://wordfaqs.ssbarnhill.com/TroublesomeLines.htm.