Plik js:
if (screen.width<=250) { document.write('<link type="text/css" href="style/250.css" media="screen" rel="stylesheet" />'); } else if ((screen.width>=250) && (screen.width<=500)) { document.write('<link type="text/css" href="style/500.css" media="screen" rel="stylesheet" />'); } else { document.write('<link type="text/css" href="style/w500.css" media="screen" rel="stylesheet" />'); }
i jak wstawiam plik do <head>