The rise of the "viewable impression" standard, which helps brands ensure their online ads are displayed in places where they can actually be seen by consumers, will entice brands to pay more for high-quality online advertising, but will mean a slowing of the sector's overall growth, Forrester reports. Ad rates will increase 76% by 2017 to $4.68 per 1,000 impressions, but annual growth in overall online ad revenues will dip below 20%.