Last week, we asked you to help a user who was seeing graph lines in all her Word documents. Eljensen was the first to respond with the most probable cause: the Gridlines option is checked. You can find this option on the View tab in the Shop group. Uncheck the option and the graph lines disappear. Gridelines is an application setting. Once you enable it, graph lines will appear on every document, including new ones, until you turn it off.
Pjunkel-pcmind offered a great reminder to check the default template. If gridlines aren’t turned on or if turning gridlines off doesn’t work, check the template file!