On-site search has become a critical component of e-commerce platforms, shaping product discovery, navigation, and purchasing decisions. While prior research has extensively examined search algorithms and information retrieval, less attention has been given to on-site search as a navigation environment in which interface design, visual guidance, and user search behavior jointly relate to search effectiveness and commercial outcomes. This study addresses this gap through three observational analyses using real-world behavioral data from a large Greek e-commerce retailer. Studies 1 and 2 employ before-and-after comparisons to examine changes associated with Search Results Page enrichment and the introduction of visual promotional guidance, while Study 3 descriptively examines generic query use and broad-to-narrow search behavior. The observed patterns show that Search Results Page enrichment coincided with lower refinement rates and improved commercial metrics, while visual guidance coincided with higher engagement and conversion-related outcomes. The behavioral analysis further indicates a strong prevalence of short, generic queries and patterns consistent with broad-to-narrow navigation. Overall, the findings suggest that on-site search performance is associated with both interface configuration and user search behavior. The study contributes real-world evidence on search as a navigation process and offers practical implications for retailers seeking to improve search-interface performance, while acknowledging the limits of observational before-and-after data for causal inference.