For example, an email program, a blog, an article that allows users
               to add comments, or applications supporting user-contributed content. Another example
               would be a page, such as a portal or news site, composed of content aggregated from
               multiple contributors, or sites that automatically insert content from other sources
               over time, such as when advertisements are inserted dynamically. In these cases, it is not possible to know at the time of original posting what the
               uncontrolled content of the pages will be. It is important to note that the uncontrolled
               content can affect the accessibility of the controlled content as well. Two options
               are available: A determination of conformance can be made based on best knowledge.