Making pages readable
Most readability problems come from a handful of settings. Fixing them takes minutes and pays off on every device.
Line length
Aim for roughly 60 to 75 characters per line. Longer lines tire the eye as it travels back to the start of the next one; shorter ones break the rhythm of reading. A container of around 680 pixels does the job for body text.
Contrast and size
Dark gray on an off-white background is easier on the eyes than pure black on pure white. Keep body text at 16 pixels or larger and let the browser scale it when the reader asks for it.
Spacing
A line height between 1.5 and 1.7 gives text room to breathe. Add generous space above headings so sections are clearly separated, and keep paragraphs short.
System fonts
Fonts that already exist on the reader's device load instantly and look native. For most notes and articles, they are a perfectly good choice.