It used to be, in Joomla 1.5, that if you wanted to see the module positions you can either click on the Preview button in the Template editable area, or add ?tp=1 to the end of your URL to see the different module positions from the front-end of your website.
However, for security purposes,since Joomla 2.5, you must enable this option in the back-end first. If you are in the Template Manager> Template tab, you will see the Preview link is disabled.
To enable it:
- log in to the back-end
- go to Extensions>Template Manager
- Click on Options in the upper right corner of the page
- Set Preview Module Positions to Enabled
- now the Preview links are enabled from the back-end. Click on it to see the module positions of the template you are using
- To see them from the front end, add ?tp=1 to the end of your URL and you will see an overlay of the modules on your template
- It is possible some modules are not visible because if a template defines those module positions as conditional on there being modules enabled in that position, it may not show up.
It is recommended that after you are done with development, you disable it again.