As a joomla developer, at times one may have a need to find the exact module positions in the template so that while changing the module position it doesn’t break the normal template structure. So to know the exact positions one can append ?tp=1 to the url of the joomla site..
For e.g:
If your site url is http://yoursite.com/, then replace it by http://yoursite.com/?tp=1
Now you should find all the module positions.

If you don’t have joomla installed, you can check it at http://www.joomla.org/?tp=1