During web search and browsing, people often accept misinformation due to their inattention to information credibility and biases. To obtain correct web information and support effective decision making, it is important to enhance searcher credibility assessment and develop algorithms to detect suspicious information. In this paper, we investigate how credibility alarms for web search results affect searcher behavior and decision making in information access systems. This study focuses on disputed topic suggestion as a credibility alarm approach. We conducted an online user study in which 92 participants performed a search task for health information. Through log analysis and user surveys, we confirmed the following. (1) Disputed topic suggestion in a search results list makes participants spend more time browsing pages than ordinary search conditions, thereby promoting careful information seeking. (2) Disputed topic suggestion during web browsing does not change participant behaviors but works as complementary information. This study contributes to system designs to enhance user engagement in critical and careful information seeking.