The Flash zombie will not die. Much has been made over the years of the death of the tech, which is growing long in the tooth and has more than its share of performance and security issues. Digital advertising, however, have helped keep it alive. Over 90 percent of rich-media impressions in the first quarter were from Flash-based banners. Blame institutional inertia: Agencies say that Flash is what they know, which is why it has been so hard to get them to move onto HTML 5, Flash’s successor.