In March, Gisele Navarro watched Google Search traffic to her Web site, HouseFresh, disappear. HouseFresh evaluates and reviews air purifiers. Her husband, Danny Ashton, launched the site in 2020, when the pandemic created a spike in demand for air purification, and at its peak the business had fifteen paid contributors. (Navarro and Ashton also work together at NeoMam, a content studio that Ashton founded.) Google traffic to HouseFresh had been slowly declining since last October, but the recen...