"If your email contains multiple messages number your points to ensure they are all read. In this way, you let your recipient delete, respond, file, or forward each item individually. Moreover, in order to keep your message readable, use stone lard capitalization and spelling, skip a line between two paragraphs, and don't type in all capital letters."
From the ILI English series, Advanced 3, student's book, sixth edition, page 120
I can not understand what 'stone lard' means in this context. Can anyone help?
Please give me references for your answers too.