I'm new to WordPress and managing website coding. I have what's probably a "duh" question. I use Firebug or the Google tool to identify a piece of web content and its underlying CSS and HTML code. I can figure out the CSS as there is just one CSS stylesheet file to deal with. But how do I know which template file is being referred to in the HTML side of the screen? How do I know if the code is part of index.php, or header.php etc.?