It’s not a hack, but you may find more documentation for the equivalent preload values expressed as a <link> tag. There is (near) parity between that and the HTTP Link header. The values used in the article should work in HTML as well.

> It’s not a hack

Yeah, this isn't a hack; this is what media queries were made for.

Now, this is a hack!

You had to do this to make :hover work correctly for IE6—IE8 [1]:

    body {
      behavior: url("csshover3.htc");
    }

[1]: https://pawelgrzybek.com/internet-explorer-just-hit-the-end-...

I agree, this was not a hack. It is combined behavior from documented features (preload with media and lazy loading).