This study seeks to investigate the subtle impact that dynamic design elements in web interfaces have on users, particularly on users' decision-making and engagement. In contrast to most current research efforts, which predominantly address mobile applications, the current study aims to direct the focus on web-based environments to reveal special behavioral responses evoked by dynamic design features. The study adopts a comprehensive mixed-methods approach that encompasses qualitative and quantitative data collection techniques. This includes A/B testing on the prototypes of web interfaces, which provides the base for measuring engagement objectively from users. A very salient point here is that animations increase user retention by 30%, which shows that well-applied dynamic elements can advance the stickiness and interaction users would have with a digital platform. On the other hand, the thesis also mentions the risks related to such design elements, like the ability to cause cognitive overload and distraction in case of non-judicious use of these elements. Through the account of user behavioral analysis in response to various implementations, the research provides useful insights to web designers and developers about how to use animations and transitions judiciously for navigational intuitiveness and responsiveness without hampering web interface usability. The present research also adds to theories for UX and user interface design (UID) by promoting the balanced integration of dynamic design elements. What was brought to the forefront was that research to understand the specific impacts of these elements can lead to more effective digital environments, tailored to foster user engagement that could support efficient processes of decision making. This thesis not only fills the academic gap related to digital interaction but also provides a practical guideline for the improvement of web interface design given user behavior and technology.