Adelle, Helvetica Neue with Proxima Nova in action on coinbase.com

Under the hood

.header-1 { font-family: proxima-nova, 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 72px; font-style: normal; font-weight: normal; letter-spacing: -1px; line-height: 72px; text-transform: none; color: #FFFFFF; }
.content-1 { font-family: adelle, Georgia, 'Times New Roman', Times, serif; font-size: 20px; font-style: normal; font-weight: 200; letter-spacing: normal; line-height: 31px; text-transform: none; color: #FFFFFF; }
.content-2 { font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 16px; font-style: normal; font-weight: normal; letter-spacing: normal; line-height: 20px; text-transform: none; color: #555555; background-color: #FFFFFF; }
.content-3 { font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 16px; font-style: normal; font-weight: normal; letter-spacing: normal; line-height: 20px; text-transform: none; color: #555555; background-color: #FFFFFF; }
.content-4 { font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 16px; font-style: normal; font-weight: 500; letter-spacing: normal; line-height: 20px; text-transform: none; color: #FFFFFF; background-color: #4B6BC2; }