title: Is there a CSS ":drop-hover" pseudo-class?
body: <p>Saying I have an <code>input type="file"</code> field. One can drop a file on this <code>input</code>(like in Firefox) instead of clicking "browse" and selecting the file.</p>
  
  <p>Now, I want to customize it a bit, by changing the field's background color when one is about to drop a file in the <code>input</code>. I cannot really use <code>:hover</code> since it matches even when you're not drag&amp;dropping. Is there a CSS (pseudo-class) to do that? </p>
  
  <p>And is there a CSS way to style different if the file being dropped is not accepted and if it is? Say, if the field accepts only PNG files using <code>accept</code> attributes, I would make the field green if you're about to drop a PNG file on it, and red if that's another type of file. </p>
  
  <p>Is there a <em>CSS</em> way to do these today? Is there a planned way to do so in <em>CSS</em> (like in upcoming specs/in current specs but not implements anywhere)?</p>