<div id="mostrar_tabla">
    <form action="<?php echo $_SERVER['PHP_SELF'];?>" name="tabla_datos" id="tabla_datos" method="POST">
       <table class="table table-striped" id="tabla" name="tabla" width="600" border="2" cellspacing="3" cellpadding="3" style="font-size: 10pt">
             ...........
       </table>
    </form>
</div>

#tabla{
     display: table;
}