different "no content" message based on taxonomy vocabulary/term
Drupal 7 has a default Taxonomy Views display you can use to override the default pages.  Here are the steps:


Install Views, if you haven't already.
Go to Structure -> Views and look for the Taxonomy term view.
In the little button that says "Enable", drop it down and select
"Clone", and create a new name for the view (it defaults to "Clone
of Taxonomy term").  This will make a copy of the Taxonomy view.
Edit the view, and drop down the Advanced tab.  Add a NO RESULTS
BEHAVIOR.
Select Global: Text area.
Enter the text you want to display for no results.


Let me know if you need help beyond this.