Which CSS property controls the layout of a webpage?

The CSS property that primarily controls the layout of a webpage is the display property. This property determines how an element is rendered on the page and how it interacts with other elements. For instance, it can define whether an element is displayed as a block, inline, grid, flex container, etc. By manipulating the display property, web designers can significantly influence the overall structure and flow of page content, making it essential for layout management.

While other properties like float and position also contribute to layout control, they serve more specific purposes. Float can be used to position elements to the left or right within their container, which impacts flow, but it doesn't govern the entire layout scheme comprehensively like display does. Similarly, position affects the positioning of elements relative to their normal flow and other elements but does not provide the broader layout management facilitated by the display property. The layout property itself is not a valid CSS property, making it entirely irrelevant in this context. Thus, display is the most fundamental property for controlling layout in CSS.