Margins

Examples:

   margin:10px 5px 15px 20px;
       top margin is 10px
       right margin is 5px
       bottom margin is 15px
       left margin is 20px

   margin:10px 5px 15px;
       top margin is 10px
       right and left margins are 5px
       bottom margin is 15px

   margin:10px 5px;
       top and bottom margins are 10px
       right and left margins are 5px

   margin:10px;
       all four margins are 10px