I can't believe I didn't see that error!
Forgot the MySQL_QUERY around the variable!!! Here's the correct..
<?
mysql_connect("xx","xx","xx") or die (mysql_error()); //connect to db
mysql_select_db("xx") or die (mysql_error()); //select db
if (($_REQUEST['id'])) {
$id = $_REQUEST['id'];
$get = mysql_query("SELECT * FROM sites WHERE id = $id");
$site = mysql_fetch_array($get);
$old_in = $site['in'];
$new_in = $site['in'] + 1;
$update = "UPDATE sites SET `out`='$new_in' WHERE id='$id'";
mysql_query($update) or die (mysql_error());
echo "redirecting to the website you requested..";
echo '<META HTTP-EQUIV=Refresh CONTENT="2; URL='.$url.'">';
}
else {
header("Location: http://www.google.com/");
}
?>