Examples of websites using
Kepler Std
(Kepler Std is a serif font designed by Robert Slimbach and published by Adobe. It is available in multiple styles, with various weights and matching italics)
with
Helvetica
(Helvetica is a sans serif font designed by Max Miedinger, Linotype Design Studio, and released by Linotype in 1957. It is available in a wide range of styles and weights)
