Abstract: Methods, systems, and apparatus, including computer program products, for fractional download of content pages in a data network including one or more servers and client devices. A single page layout is identified for a content page to be downloaded from a server to a client device in the data network. The single page layout defines a geometrical arrangement of content reservation areas for presenting respective content elements from the entire content page. For example, the single page layout can include hierarchically arranged containers. An active portion is identified in the single page layout, where the active portion corresponds to a display area for displaying the content page on a display unit of the client device. Content elements are provided to the client device for the content reservation areas in the active portion of the single page layout without providing content elements for content reservation areas that are outside of the active portion.