Using eye-tracking field experiments, we examine the dynamics underlying consumers' attention-allocation behaviors in online search, with focus on attention adjustment, attention renewal, and equilibrium seeking. In particular, we probed into how consumers' e-commerce search behaviors vary when they are exposed to an advertisement during a search and when they are not. The findings from the two separate experiments suggest that consumers' attention span decreases exponentially, instead of linearly, as they maneuver from the top to the bottom of a search result webpage. The total number of available options significantly influences the speed and pattern of attention decay. However, attention decay does not simply move in the direction of depletion but can be refreshed and renewed upon encountering attention-diverting ad stimuli. Although ad stimuli are often considered distracting and worthless, they can produce positive effects when positioned in the middle of a search results listing, where a consumer's attention resources are rejuvenated by ads. Finally, because of consumers' propensity to seek equilibrium, attention decay occurs more rapidly after, rather than before, attention renewal. We extend the literature on the mere categorization effect by investigating how ad stimuli structurally separate search choices into mental categories and diminish on-going attention decay patterns.