资料来源 : Free On-Line Dictionary of Computing

META element
     
         An {element}, with tag name of "META",
        expressing {meta-data} about a given {HTML} document.  HTML
        standards do not require that documents have META elements;
        but if META elements occur, they must be inside the document's
        HEAD element.
     
        The META element can be used to identify properties of a
        document (e.g., author, expiration date, a list of key words,
        etc.) and assign values to those properties, typically by
        specifying a NAME {attribute} (to name the property) and a
        CONTENT attribute (to assign a value for that property).  The
        HTML 4 specification doesn't standardise particular NAME
        properties or CONTENT values; but it is conventional to use a
        "Description" property to convey a short summary of the
        document, and a "Keywords" property to provide a list of
        {keywords} relevant to the document, as in:
     
         
         
     
        META elements with HTTP-EQUIV and CONTENT attributes can
        simulate the effect of {HTTP} header lines, as in:
     
         
         
     
        Other properties may be application-specific.  For example,
        the {Robots Exclusion
        (http://info.webcrawler.com/mak/projects/robots/norobots.html)}.
        standard uses the "robots" property for asserting that the
        given document should not be indexed by robots, nor should
        links in it be followed:
     
         
     
        (2001-02-07)