This is a quick tip for Drupal 7 to show how easy it is to see what is the Node ID of a given node if you use the module Pathauto or something else to create alternate URLs for your nodes.

It is quite simple really, but not the most obvious. When you first install Drupal and create nodes (with Clean URLs turned on), your node URLs look like something this: www.example.com/node/1(1 is in this case the Node ID). But what if you start using path aliases and the URL for Node 1 turns into www.example.com/content/some-title?

Easy. Go to Content and filter downt to find the content you want to see the Node ID for and hover over the Edit link. Look down to see the hyperlink your browser tells you it will follow if you click on Edit. 

There in the link you should see the URL to the node in its original [node/number] form. 

Hope this helps!