11. A system for modifying a display of content that includes a first portion that was previously displayed to a user and that is capable of including a portion that was part of the content at the time the first portion was previously displayed to the user, but that has yet to be displayed to the user, the system comprising: at least one processor; at least one interface configured or designed to provide a communication link to at least one other network device in the data network; and memory including instructions that, when executed by the at least one processor, cause the system to: receive a request for content to be displayed to a user, the content being associated with a markup document that is associated with a first URL such that the content is retrievable by accessing the markup document from a location specified by the first URL; retrieve the content associated with the markup document; determine difference information indicating any differences between a previous version and a current version of the markup document, the previous version having been previously presented to the user; access user activity information to determine portions of the markup document that were previously displayed to the user; based on the difference information and the user activity information, determine portions of the current version of the markup document that have not previously been displayed to the user; provide the markup document for display to the user at a client system, the content of the markup document including one or more intra page bookmarks indicating portions of content that were not previously displayed to the user; and enable the user to use the intra page bookmarks to locate the portions of the markup document that were not previously displayed; enable the user to manually insert intra page bookmarks in the markup document allowing the user to start at a desired location after closing the markup document; and enable the user to selectively choose to display or not display the intra page bookmarks.
15. The system of claim 11 , wherein the markup document corresponds to a weblog page.