List boxes can often be a source of performance degradation due to their elaborate configurations and lengthy lookup times that may have to occur at a cell level. Even if disabled, on the loading of the page, the cell value must be looked up to display to the user. If several list boxes are located on the Horizontal View, page load time can be severely inflated. An easy solution is to have a read-only view-level resolution of the list source (assuming it is a view in the same database) on the Horizontal View, and an editable list box on the Vertical View. This keeps the description field visible on the Horizontal View of the page, making it filterable and searchable, while greatly increasing performance.
Alternatively, the list box on the Horizontal View can itself be simplified when it is disabled. There is no need to include a complex WHERE clause that may be present in the list box configuration, if it is only meant to resolve values and not restrict user input or security. Even this simple change can improve page load.