It's possible to visualize all modules set on a template by calling the "tp=1" query string on the front-end.
http://www.example.com/index.php?tp=1
Joomla 2.5 and Joomla 3.x will show the template positions with ?tp=1 or &tp=1 if the Preview Module Positions mode in the Template Manager has been Enabled:
- Extensions → Template Manager then click the Options button in the toolbar.
- Under the Templates Tab, make sure Preview Module Positions is set to Enabled.