HTML

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "https://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
  <html xmlns="https://www.w3.org/1999/xhtml" xml:lang="pt-br">
  <head>
  <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />
  <title>Layout CSS com duas colunas - Exemplo 1</title>
  </head>
  <body>
  
  <div id="tudo">
  
  <div id="topo">TOPO</div>
  
  <div id="principal">COLUNA PRINCIPAL</div>
  
  <div id="navegacao">COLUNA NAVEGAÇÃO</div>
  
  <div id="rodape">RODAPE</div>
  
  </div>
  
  </body>
  </html>

RENDERIZAÇÃO:

TOPO
COLUNA PRINCIPAL
RODAPE