I have a little doubt about the alignment between these two table
<table id="tableCabecVendasML">
and <table id="tableDadosVendasML">
HTML and CSS
html {
margin:0;
padding:0;
height:100%;
}
body {
margin:0;
padding:0;
height:100%;
}
#divAreaSite {
background: #cad5c5;
width: 100%;
height: 100%;
overflow-y: hidden;
}
#divAreaConteudo {
background: #abb4a6;
margin-left: 5%;
margin-right: 5%;
height: 100%;
}
#LinhaCabec {
height: 20px;
width: 100%;
}
#tableEstrutura, td,tr {
border: 1px solid black;
}
#tableEstrutura {
border-collapse: collapse;
width: 100%;
height: 100%;
}
#LinhaTitulo {
background-color: #0fcc15;
height: 20px;
}
#LinhaMenu {
background-color: #cc71cc;
height: 20px;
}
#LinhaRodape {
background-color: #cc71cc;
height: 20px;
}
#AreaDados {
background-color: #cccc8e;
height: 100%;
overflow-y: auto;
}
#tableCabecVendasML {
width: 100%;
//position: relative;
}
#tableDadosVendasML {
width: 100%;
//height: 100%;
}
.ColCodigo {
width: 20%;
}
.ColNomeCliente {
width: 20%;
}
.ColData {
width: 20%;
}
<!DOCTYPE html>
<html lang="pt-br">
<header>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1">
<title>Vendas Mercado Livre</title>
<link rel="stylesheet" type="text/css" href="css/ver_vendas_mercadolivre.css">
</header>
<body>
<div id="divAreaSite">
<div id="divAreaConteudo">
<table id="tableEstrutura">
<tr>
<td id="LinhaTitulo" colspan="2">Titulo</td>
</tr>
<tr>
<td id="LinhaMenu" colspan="2">Menu</td>
</tr>
<tr id="LinhaCabec">
<td rowspan="2">menu <br> Lateral </td>
<td>
<table id="tableCabecVendasML">
<tr>
<td class="ColCodigo"> Código </td>
<td class="ColNomeCliente"> Nome do Clinte </td>
<td class="ColData"> Data</td>
</tr>
</table>
</td>
</tr>
<tr>
<td>
<div id="AreaDados">
<table id="tableDadosVendasML">
<tr>
<td class="ColCodigo"> AAAAAAAAA</td>
<td class="ColNomeCliente"> Coluna 2</td>
<td class="ColData"> Coluna 3</td>
</tr>
<tr>
<td class="ColCodigo"> 12121212</td>
<td class="ColNomeCliente"> Coluna 2</td>
<td class="ColData"> Coluna 3</td>
</tr>
<tr>
<td class="ColCodigo"> sdasdsd</td>
<td class="ColNomeCliente"> Coluna 2</td>
<td class="ColData"> Coluna 3</td>
</tr>
<tr>
<td class="ColCodigo"> sdasdsd</td>
<td class="ColNomeCliente"> Coluna 2</td>
<td class="ColData"> Coluna 3</td>
</tr>
<tr>
<td class="ColCodigo"> 12121212</td>
<td class="ColNomeCliente"> Coluna 2</td>
<td class="ColData"> Coluna 3</td>
</tr>
<tr>
<td class="ColCodigo"> sdasdsd</td>
<td class="ColNomeCliente"> Coluna 2</td>
<td class="ColData"> Coluna 3</td>
</tr>
<tr>
<td class="ColCodigo"> sdasdsd</td>
<td class="ColNomeCliente"> Coluna 2</td>
<td class="ColData"> Coluna 3</td>
</tr>
<tr>
<td class="ColCodigo"> 12121212</td>
<td class="ColNomeCliente"> Coluna 2</td>
<td class="ColData"> Coluna 3</td>
</tr>
<tr>
<td class="ColCodigo"> sdasdsd</td>
<td class="ColNomeCliente"> Coluna 2</td>
<td class="ColData"> Coluna 3</td>
</tr>
<tr>
<td class="ColCodigo"> sdasdsd</td>
<td class="ColNomeCliente"> Coluna 2</td>
<td class="ColData"> Coluna 3</td>
</tr>
<tr>
<td class="ColCodigo"> 12121212</td>
<td class="ColNomeCliente"> Coluna 2</td>
<td class="ColData"> Coluna 3</td>
</tr>
<tr>
<td class="ColCodigo"> sdasdsd</td>
<td class="ColNomeCliente"> Coluna 2</td>
<td class="ColData"> Coluna 3</td>
</tr>
<tr>
<td class="ColCodigo"> 12121212</td>
<td class="ColNomeCliente"> Coluna 2</td>
<td class="ColData"> Coluna 3</td>
</tr>
<tr>
<td class="ColCodigo"> sdasdsd</td>
<td class="ColNomeCliente"> Coluna 2</td>
<td class="ColData"> Coluna 3</td>
</tr>
<tr>
<td class="ColCodigo"> sdasdsd</td>
<td class="ColNomeCliente"> Coluna 2</td>
<td class="ColData"> Coluna 3</td>
</tr>
<tr>
<td class="ColCodigo"> 12121212</td>
<td class="ColNomeCliente"> Coluna 2</td>
<td class="ColData"> Coluna 3</td>
</tr>
<tr>
<td class="ColCodigo"> sdasdsd</td>
<td class="ColNomeCliente"> Coluna 2</td>
<td class="ColData"> Coluna 3</td>
</tr>
<tr>
<td class="ColCodigo"> sdasdsd</td>
<td class="ColNomeCliente"> Coluna 2</td>
<td class="ColData"> Coluna 3</td>
</tr>
<tr>
<td class="ColCodigo"> 12121212</td>
<td class="ColNomeCliente"> Coluna 2</td>
<td class="ColData"> Coluna 3</td>
</tr>
<tr>
<td class="ColCodigo"> sdasdsd</td>
<td class="ColNomeCliente"> Coluna 2</td>
<td class="ColData"> Coluna 3</td>
</tr>
<tr>
<td class="ColCodigo"> sdasdsd</td>
<td class="ColNomeCliente"> Coluna 2</td>
<td class="ColData"> Coluna 3</td>
</tr>
<tr>
<td class="ColCodigo"> 12121212</td>
<td class="ColNomeCliente"> Coluna 2</td>
<td class="ColData"> Coluna 3</td>
</tr>
<tr>
<td class="ColCodigo"> sdasdsd</td>
<td class="ColNomeCliente"> Coluna 2</td>
<td class="ColData"> Coluna 3</td>
</tr>
<tr>
<td class="ColCodigo"> 12121212</td>
<td class="ColNomeCliente"> Coluna 2</td>
<td class="ColData"> Coluna 3</td>
</tr>
<tr>
<td class="ColCodigo"> sdasdsd</td>
<td class="ColNomeCliente"> Coluna 2</td>
<td class="ColData"> Coluna 3</td>
</tr>
<tr>
<td class="ColCodigo"> sdasdsd</td>
<td class="ColNomeCliente"> Coluna 2</td>
<td class="ColData"> Coluna 3</td>
</tr>
<tr>
<td class="ColCodigo"> 12121212</td>
<td class="ColNomeCliente"> Coluna 2</td>
<td class="ColData"> Coluna 3</td>
</tr>
<tr>
<td class="ColCodigo"> sdasdsd</td>
<td class="ColNomeCliente"> Coluna 2</td>
<td class="ColData"> Coluna 3</td>
</tr>
<tr>
<td class="ColCodigo"> sdasdsd</td>
<td class="ColNomeCliente"> Coluna 2</td>
<td class="ColData"> Coluna 3</td>
</tr>
<tr>
<td class="ColCodigo"> 12121212</td>
<td class="ColNomeCliente"> Coluna 2</td>
<td class="ColData"> Coluna 3</td>
</tr>
<tr>
<td class="ColCodigo"> sdasdsd</td>
<td class="ColNomeCliente"> Coluna 2</td>
<td class="ColData"> Coluna 3</td>
</tr>
<tr>
<td class="ColCodigo"> sdasdsd</td>
<td class="ColNomeCliente"> Coluna 2</td>
<td class="ColData"> Coluna 3</td>
</tr>
<tr>
<td class="ColCodigo"> 12121212</td>
<td class="ColNomeCliente"> Coluna 2</td>
<td class="ColData"> Coluna 3</td>
</tr>
<tr>
<td class="ColCodigo"> sdasdsd</td>
<td class="ColNomeCliente"> Coluna 2</td>
<td class="ColData"> Coluna 3</td>
</tr>
<tr>
<td class="ColCodigo"> sdasdsd</td>
<td class="ColNomeCliente"> Coluna 2</td>
<td class="ColData"> The END </td>
</tr>
</table>
</div>
</td>
</tr>
<tr>
<td id="LinhaRodape" colspan="2">Rodape</td>
</tr>
</table>
</div>
</div>
</body>
</html>