Examples of websites using
Avenir
(Avenir is a sans-serif font designed by Adrian Frutiger and Nadine Chahine, released by Linotype in 1988. It features clean and modern letterforms and is available in multiple weights and styles)
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)