It's The Ad Contrarian's "The Universal and The Transient in Advertising."
The basic gist of it is this: current and future advertisers should know the history of their field. But there's a lot more than that and it's really well written.
During my first internship I started to realize a lot of the problems we think of as new today are the same problems they faced decades ago. The platforms have changed and the field has gotten bigger but if you look at the rhetoric of the past you will see how closely it resembles the present.
It should stand that the most important thing we can do today is learn from the past. Don't obsess over it, wish that things "were the way they once were," decry all new technology. But learn from it. Even if it's learning about the names dropped in Mad Men that's a good place to start.
Pick up a book, or an e-book, and learn some history. It's a great investment in yourself.
Here's a comment I really liked from that post: