Helvetica is not pre-installed on Windows PCs and other non Apple devices. You need to include Sans-Serif in your CSS - so the default sans serif font is picke

Helvetica is not pre-installed on Windows PCs and other non Apple devices. You need to include Sans-Serif in your CSS - so the default sans serif font is picked for non Apple devices. Or be more specific and list Arial, Segoe UI, Calibri etc There are still tons of Windows users out there, so worth checking on non Apple devices.