Definition of "fragment identifier"
A fragment identifier is a string of characters that is frequently used to identify a specific location within an HTML page. In a URI, if the identifier contains any spaces or special characters, they must be escaped using percent escape codes as explained in the URL-encoding tutorial.
Fragment identifiers are defined by RFC 2396 and in general can be appended to a URI to be used after the resource has been retrieved. For HTML documents, the browser will retrieve the document specified by the URI then automatically scroll the browser window if necessary so the specified location on the page appears in the currently visible area. If the href
attribute of a hyperlink consists of just a fragment identifier with no URI, the browser will scroll the current page to the specified location.