Described is a technology by which a piece of content is selected from among at least two pieces of content in response to a request to return content. The selection is based on an evaluation of current state data against the properties/characteristics of the content. For example, the state data may define a currently available size; each piece of content has associated size properties (e.g., height and width ranges) that can be matched in the selection process. In a layout system, a parent container may request content from a child container that is associated with the selection process. The selection process may, for example, evaluate the child's pieces of content in an evaluation order, with the first appropriate matching piece of content selected. If no content matches, a default piece of content, or a code that indicates that no content is to be shown, is returned.