The field of human–computer interaction is constantly evolving and facing new challenges. In this study, we propose an experimental method for designing e-commerce user interfaces with varying levels of aesthetics and usability while maintaining a similar level of user experience. The method is based on the Deming Cycle and Nielsen’s framework for design principles. Four e-commerce websites were designed with low/high levels of aesthetics and usability. Based on 160 surveys, the experimental results demonstrated that it is possible to design user interfaces with varying levels of aesthetics and usability while maintaining a similar level of user design perception. Our findings suggest that usability is more crucial than aesthetics in enhancing user experience, which aligns with previous studies. We also emphasize considering aesthetics and usability in UI design and propose the principle “What You Design Is What You Get” (WYDISWYG) as a foundation for future research. Among the evaluated websites, Website1 (the best design) achieved the highest UI quality, with users perceiving it positively at an impressive rate of almost 0.91 percent. In contrast, Website4 (the worst design) had the lowest UI quality, receiving a perception score of only 0.38 percent. The websites designed with a combination of aesthetics and usability, Website2 and Website3, garnered different perception values of 0.79 and 0.51, respectively. While this study has some limitations, such as the subjective selection of features and the focus on e-commerce websites only, it provides a starting point for further investigation into the selection of design principles, consideration of other website domains, and clarification of users’ perception of UI elements to align with Nielsen’s principles.