Use Template Path Hints

When you want to figure out which Block or phtml file a problem is occurring in, you can turn on template hints and 
see the information right on the browser. It's awesome, so if you haven't tried it, try it right now.

First, you NEED to select the store view you want to show the hints on. If you don't, the configuration option won't 

System > Configuration > Advanced > Developer > Debug > Template Path Hints and/or Add Block Names to Hints

By default, there is no way to turn on hints for the Admin Panel, see the links. 
To Turn on hints for Admin Panel:

Admin templates hint

# add INSERT INTO core_config_data (scope, scope_id, path, value) 
VALUES ('default', 0, 'dev/debug/template_hints', 1), 
('default', 0, 'dev/debug/template_hints_blocks', 1); 

# changes SELECT * FROM core_config_data 
WHERE path LIKE "%template_hints%" AND scope="default";