This work deals with the research of subliminal messages in Internet advertising. Subliminal messages are hidden pieces of information conveyed below the threshold of conscious perception, used to unconsciously influence individuals' behavior. The aim of this paper is to analyze the presence and impact of subliminal messages in online advertising and to understand their effect on consumers. The paper is divided into six sections. The first section deals with defining subliminal messages, explaining what they are and how to recognize them. The second section covers their history and development, exploring their origins and evolution. The third section investigates subliminal perception, explaining how people unconsciously process subliminal messages and how these messages affect their subconscious. The fourth section defines advertising and describes its development throughout history. After familiarizing with the terminology necessary for further understanding of the topic, the fifth section specifically examines the use of subliminal messages in advertising, providing examples and analyses. It analyzes the impact of subliminal messages on consumers, exploring how they can shape customer perception and behavior. It also describes various techniques used to implement subliminal messages. The sixth section is dedicated to online advertising and its forms, and explores the use of subliminal messages on social media, a topic that is still not widely discussed. The paper concludes with a summary that encapsulates the explored topic and key information found through review and analysis. The paper utilizes selected literature and examples for the purpose of analyzing the topic of subliminal messages in online advertising. Concrete examples of advertising using subliminal messages are also presented to provide insight into their actual effects and potential.