css3-mediaqueries-js is probably what you are looking for: this script emulates media queries. However (from the script’s site) it “doesn’t work on @import
ed stylesheets (which you shouldn’t use anyway for performance reasons). Also won’t listen to the media attribute of the <link>
and <style>
elements”.
In the same vein you have the simpler Respond.js, which enables only min-width
and max-width
media queries.