Popcorn idea!
First, let me explain the title: I have these wild inspirationally inventive moments when I come up with a solution to a problem during the course of something not directly related to the problem or the solution.
This solution: Cache validation. Today's web browsers know that things like high-res blog background pictures generally don't change, and may be saved on the hard drive instead of always re-fetching them. Servers are generally responsible for telling the browser when something (image, javascript, css, etc) expires or changes. But we already have technology for determining if object A is the same as object B without moving a ton of data: hashes. Why not take a SHA-1 hash of every file your site hosts, and in the HTTP(S) protocol include that as one if the first parameters the browser reads? if the hash matches the cache's hash, the browser can ignore the server and load from the hard drive. Otherwise, the browser can continue loading the data being sent to it.
I haven't yet done any googling to see if this is already implemented, but my personal bias is that it hasn't.