User interface design (a.k.a., UI design) has recently become an important pillar in application development, as it directly influences a user’s experience. The color scheme, proximity of elements, and text styling all come together to accentuate a certain look and feel. While 4D already has an integrated form editor, it can take time to manually configure the style properties for multiple form elements, especially across various pages and forms. With the style sheet feature in project mode, the CSS language can be used to directly style forms in a more streamlined fashion. This technical note will go over how to implement external style sheets for project-based applications.