Web personalization involves tailoring website content and advertisements to a user's preferences and behavior. It began in the mid-1990s and works by tracking a user's explicit preferences or implicit behaviors to serve personalized recommendations. Personalization can increase online conversion rates and save users time by focusing on relevant information. However, it also risks lack of relevance, credibility, privacy, or annoyance to users. Experiments showed that after browsing but not buying items, personalized recommendations for similar products were displayed upon the user's return to the site.