Thanks, Tex2002ans.
I understand media queries and adobe-hyphenate. What I meant was, I use them for my own purposes, but it always throws a validation error, which I ignore. Then the "invalid" css succeeds in making my ereaders do what I want them to.
I was just wondering if there was a different media query that wouldn't throw a css validation error, but it looks like "amzn-kf8" is the proper media type for kf8, according to the Kindle Publishing Guidelines.
And if adobe-hyphenate is the proper css for ADE/RMSDK, that answers that question as well.
But at least I got rid of the widows/orphans validation error