var cssName;

     if( screen.availWidth < 850 ) {  
        cssName = 'lowres.css';
      } 
	else if( screen.availWidth > 1000 ) {
          cssName = 'highres.css';
        } 
	else {
          cssName = 'lowres.css';
	}
      document.write('<link rel="StyleSheet" href="c/' + cssName + '" type="text/css" />');