OK; I have tried like this, but I've got NO error message, but echoing $Inmo gives nothing.
<?php
//page2
session_start();
if (session_is_registered('usuario')){
}
else{
header("Location: acceso6.html?errorusuario=si");
}
$session= session_id();
$base="";
$conexion=mysql_connect("","","");
mysql_select_db($base,$conexion);
$pegar2 = "SELECT Inmo FROM Sesiones WHERE Sesion='$session'";
mysql_query($pegar2);
//$row = mysql_fetch_array($pegar2);
$Inmo = $row["Inmo"];
?>