Many times you read an article or a blog post that states as a fact something you know to be wrong.
A browser extension and a server side service that enables you to leave a comment on any site. This comment should be reasoned and if possible backed up by reliable data with link and attribution. These corrections will be approved by editors before they are visible. The approved comments will be visible to others using the same browser extension, or to all if the website itself chooses to incorporate the system (1 line of code in their HTML source.)