Add Helvetica font stack as fallback for Open Sans
Add Helvetica font stack as fallback for Open Sans

If Open Sans doesn’t load, use Helvetica rather than default user agent
font as fallback.
mesosphere/marathon-ui,Raffo/marathon-ui,janisz/marathon-ui,quamilek/marathon-ui,janisz/marathon-ui,cribalik/marathon-ui,Raffo/marathon-ui,watonyweng/marathon-ui,pierlo-upitup/marathon-ui,pierlo-upitup/marathon-ui,watonyweng/marathon-ui,cribalik/marathon-ui,yp-engineering/marathon-ui,Kosta-Github/marathon-ui,yp-engineering/marathon-ui,mesosphere/marathon-ui,quamilek/marathon-ui,Kosta-Github/marathon-ui