Yahoo email accounts were blocked last week for some users unless they opted to switch off their ad blockers. According to The New York Times, the move is part of an experiment to combat ad-blocking software, which allows users to browse the Web free of online advertising. “At Yahoo, we are continually developing and testing new product experiences,” said Anne Yeh, a Yahoo spokeswoman. “This is a test we’re running for a small number of Yahoo Mail users in the U.S.” The Yahoo test highlights the ongoing debate over ad blocking between publishers, advertisers and tech companies — and the need for viable alternatives to display ads (such as native advertising) for both desktop and mobile.