taxonomy_node_get_terms(arg(1)) kills layout in page.tpl.php
taxonomy_node_get_terms() needs a node object as the first argument; arg() returns a part of the URL (which is just a string).

You can use the menu_get_object() function to get the current node (if available) so it would be easier to use that:

$node = menu_get_object();
if ($node) {
  $tax = taxonomy_node_get_terms($node);
}