Changing Title Tags for entire Site

A few years ago I changed it so that the exact same title tag would appear for every page of my site. 

It only affects some of my templates, and not the main template that I have been using for the last few years.

However, now I want to get rid of the change that I made and I can't remember what file I edited.

Does anybody have any idea what file I edited to give all the pages of my entire site the same title tag.

Thanks!!!

My guess would be _header.html

Most likely you changed

<title>__page_header__</title>

Which is the default to something like

<title>My Kick A$$ Title</title>

But that is just a guess. You really should be documenting your changes somewhere.