Joomla 1.5 Module Positions
1. Check the module map on your website using this code: http://yourwebsiteurl.com/index.php?tp=1
Other joomla versions
First of all you have to activate in the Joomla backend this feature.
1. Go to Extensions > Template Manager
2. Click on the Options button at the top right (you will see a pop up window)
3. Enable the Preview Module Positions and click Save.
4. Check the module map on your website using this code: http://yourwebsiteurl.com/index.php?tp=1