This could easily be stopped by a change in browser behavior. If web browsers downloaded contacted every address specified with `url()` automatically on page lo

This could easily be stopped by a change in browser behavior. If web browsers downloaded contacted every address specified with `url()` automatically on page load, without considering the conditions, this type of conditional requests would be impossible. Conceivably, you could solve it through a simple browser extension that looks through all of the page’s stylesheets and calls all URLs present in the CSS before the page is rendered. In an ideal implementation, though, URLs dependant on “static”, non-identifiable conditions, such as an image with `display: none`, would be left alone.