The 'show' attribute is used to communicate the desired presentation 
of the ending resource on traversal from the starting resource; it's 
value should be treated as follows: 
new - load ending resource in a new window, frame, pane, or other 
      presentation context
replace - load the resource in the same window, frame, pane, or 
          other presentation context
embed - load ending resource in place of the presentation of the 
        starting resource
other - behavior is unconstrained; examine other markup in the 
        link for hints 
none - behavior is unconstrained