Open Sans in action on c5capital.com

.header-1 { font-family: 'Open Sans'; font-size: 36px; font-style: normal; font-weight: 300; letter-spacing: 7.2px; line-height: 50.4px; text-transform: uppercase; color: #060606; }
.header-2 { font-family: 'Open Sans'; font-size: 16.8px; font-style: italic; font-weight: normal; letter-spacing: normal; line-height: 23.52px; text-transform: none; color: #060606; }
.content-1 { font-family: 'Open Sans'; font-size: 14px; font-style: normal; font-weight: 500; letter-spacing: normal; line-height: 19.6px; text-transform: none; color: #424242; }
.content-2 { font-family: 'Open Sans'; font-size: 14px; font-style: normal; font-weight: 500; letter-spacing: normal; line-height: 19.6px; text-transform: none; color: #444444; }
.content-3 { font-family: 'Open Sans'; font-size: 14px; font-style: normal; font-weight: 500; letter-spacing: normal; line-height: 19.6px; text-transform: none; color: #444444; }
Open Sans is available from Font Squirrel, Google Web Fonts, MyFonts and Typekit.
Found by @mikesten on 17 Feb 2016.

Liked by:
@mikesten @tradeandcraft @LehmanBuzon @zinjabil

Open Sans