Put Marissa Mayer in the “better ads will stop people from blocking Web ads” camp.

The Yahoo chief executive was asked about the impact of ad-blocking software on the digital ad business during a keynote session on Monday at the Interactive Advertising Bureau’s conference in New York, during Advertising Week. Ms. Mayer politely warned Internet users that they might miss advertising, and they may really miss their favorite content if online ads go away in big numbers.

Ms....