Magento – Template Path Hints
Magento is an undoubtedly deep and complex shopping cart tool, and for first-time users the sheer number of files can make finding what you’re looking for very difficult indeed. I don’t really use it anymore, but when I developed my first Magento site I found the Template Path Hints tool invaluable…

Yes, it makes a complete mess of your site during the time that it is enabled, but it shows you the exact locations of all the included phtml files on the page meaning you can find the part you need to edit quickly, simply by following the file path.
A good tip and something that I often do, is to enable it the first time you go onto your site and then go into different parts of the site, while taking a screenshot of each page. Then you’ll find that you don’t need to keep enabling it – just refer to your screenshots.
Since the embed code is not W3C Compliant – I can only give you a link to a good video showing you how to use it:
Magento Tutorial – Turn On Template Path Hints from Steve Warshaw on Vimeo.

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