1. A computer-implemented method for providing prerequisite checking in a computer system for creating a user-defined, web-based content object that is generated by the computer system, being one of a book, a document, a collection of images, a collection of musical selections, a video and a multimedia object, from a plurality of individual content entities including content for the web-based content object and stored as a plurality of hierarchically related individual content entities in a data repository as a plurality of individual file objects, some of the content entities being prerequisites to others of the content entities, the method comprising the steps of: defining the web-based content object by a list indicating the content entities from the data repository specified by a user for the web-based content object, adding or removing a selected content entity to or from the list indicating the content entities from the data repository specified by the user through a web-based user interface for the web-based content object to add or remove the selected content entity to or from the web-based content object, wherein a prerequisite content entity is associated with another content entity and designated for inclusion in each web-based content object for which that other content entity is selected and placed, and wherein designations of prerequisite content entities for content entities within the data repository are stored external of the individual file objects containing the content entities, examining the stored designations of prerequisite content entities and determining if the selected content entity has any prerequisite content entities designated for that content entity, and if so, automatically adding or removing the designated prerequisite content entities to or from the list in direct response to user interaction initiating the addition or removal of the selected content entity to add or remove the prerequisite content entities to or from the web-based content object, wherein the conditions for applying a prerequisite are defined in one or more rules, and wherein selection by the user of an entity having prerequisites causes automatic inclusion of all associated prerequisite objects complying with the conditions in a final compilation, creating a file object defining the compilation that contains a list or outline of the content entities selected, their identifiers, order and structure, and storing the file object separately in the data repository.