unwanted dashed line

The text appears surrounded by an unwanted dashed line. What can it be? How can I remove it?
P.S. Sorry for the language errors. I’m not english.

Does it look like this?

If it does, it probably means you’ve accidentally selected ‘Preserve Formatting’ – which means the format of the selected text will not be changed in the Compilation process but will appear As-Is.

All you need to do to remove it is to select the text and unselect Preserve Formatting. (Sorry, I don’t have the Windows version, so I don’t know which menu it’s on – probably the Format menu.)

Thank you very much.
Now it is OK!!!