With the increasing expansion of e-commerce and the changing behavior of consumers towards online shopping, online sales networks have become one of the most important platforms for interaction between businesses and customers. In the meantime, digital advertising plays a key role in attracting customers, increasing sales, and strengthening brand positioning. Given the intense competition among online stores, the effectiveness of advertising as one of the strategic components of marketing requires careful and scientific examination. The main objective of this research was to identify and prioritize the key factors affecting the effectiveness of advertising in the context of online sales networks; an area that has gained increasing strategic importance in the field of digital marketing due to the increasing expansion of e-commerce. In order to achieve this goal, a qualitative approach was used and research data was collected through semi-structured interviews with 12 selected experts in the field of digital marketing, including marketing managers, branding consultants, and online advertising specialists. Data analysis was conducted using the fuzzy Delphi method to extract meaningful prioritization of factors through gradual convergence of expert opinions and reduction of subjective uncertainties. The research findings showed that "the suitability of advertising content with the real and perceived needs of the customer" was identified as the most important factor affecting the effectiveness of digital advertising. From the perspective of consumer psychology, this factor has a direct impact on the process of understanding the message and the desire to interact with it. In second place was "visual attractiveness of the advertisement", which includes graphic design, color scheme, arrangement of visual elements and coordination of the advertising style with the brand identity. The third factor was "interactivity of the advertisement", which refers to the interactive capabilities of the advertising message; Including the ability to click, respond, share, or personalize the message by the audience. Other important factors identified were: "brand trust" which acts as a mediating variable in enhancing the acceptance of the advertising message, and "timing and time position of the ad display" which can play a key role in optimizing the attention and response of the audience. The results of this research can be used as a conceptual and operational model for designers of digital advertising campaigns. By emphasizing the alignment between the advertising message and the needs of the target audience, this framework will play an important role in increasing conversion rates, improving user interaction with the brand, and ultimately improving the return on advertising investment.