In your html
<table class="table1">
<tr>
<td>
...
</table>
<table class="table2">
<tr>
<td>
...
</table>
In your css:
table.table1 {...}
table.table1 tr {...}
table.table1 td {...}
table.table2 {...}
table.table2 tr {...}
table.table2 td {...}