MediaWiki:Common.css

 table.wikitable, table.prettytable { 
     margin: 1em 1em 1em 0;
     background: #f9f9f9;
     border: 1px solid #aaaaaa;
 }

 table.wikitable th, table.wikitable td, table.prettytable th, table.prettytable td { 
     border: 1px solid #aaaaaa;
     padding: 0.2em;
 }

 table.wikitable th, table.prettytable th { 
     background: #f2f2f2;
 }

 table.wikitable caption, table.prettytable caption { 
     margin-right: inherit;
     margin-left: inherit;
     font-weight: 700;
 }

 table.prettytable code, table.wikitable code { 
     background-color: transparent;
 }