Hi daniele,
probably you are referring to an object, not a proper node.
In this case node_id doesn't work normally. Try object_id (or contentobject_id) instead.
Doing a "show" in most cases help to find the correct sintax:
{$__YOUR-OBJECT-OR-NODE__|attribute(show)}
ciao
<i>"Vinum bibant homines, animalia cetera fontes..."</i>
nnnnn maybe you don't understand where is the problem. For example, if you are in the advanced search template you aren't in any node because this is the ezpublish's funcinality, my question is how can I check if I'm in this "no node" templates???
PS: I'm very happy that there are an Italian developer!