It's never a good idea to paste copy into Zencart from any WYSIWYG editor, especially Front Page and Word. Such programs add a lot of extraneous styling that can conflict with what Zencart is trying to do, and may be the reason for your extra lines.

Better to paste (or enter) your copy as plain text and style it in the stylesheet, or use the HTML editor in the define pages editor to enter the copy in the first place.