m; clear: both; /* clearance is negative (see 8.3.1 and 9.5.1) */ }

   /* line ten and eleven: containing block for abs pos */
   .smile div { margin-top: 0.25em; background: black; width: 12em; height: 2em; position: relative; bottom: -1em; }
   .smile div div { position: absolute; top: 0; right: 1em; width: auto; height: 0; margin: 0; border: yellow solid 1em; }

   /* smile (over lines ten and eleven): backgrounds behind borders, inheritance of 'float', nested floats, negative heights */
   .smile div d