Serif type on screens

For a decade, screens were too coarse for serifs and we learned to read in sans. Then pixels got small, and the reason went away while the habit stayed.

Use the fonts already there

Every system ships a good serif. A stack like this one costs nothing to download and looks deliberate everywhere:

font-family: Charter, "Bitstream Charter", "Iowan Old Style",
  "Sitka Text", Cambria, Georgia, serif;

Set the measure, then the size

A line of 60 to 75 characters is the oldest rule in typography for a reason. Choose the column width first, then the size that fills it, then a line height around 1.6.

Serifs will not save a page with a 120 character line. A good measure will save almost any typeface.