var agt = navigator.userAgent.toLowerCase();

if (agt.indexOf("ie 6") > -1) {
    //	alert("ie 6");
    document.write("<link rel='stylesheet' href='css/ie6.css' type='text/css' media='screen' />");
}
else if (agt.indexOf("ie 7") > -1) {
    //alert("ie 7");
    document.write("<link rel='stylesheet' href='css/ie7.css' type='text/css' media='screen' />");
}
else if (agt.indexOf("ie 8") > -1) {
    //alert("ie 7");
    document.write("<link rel='stylesheet' href='css/ie8.css' type='text/css' media='screen' />");
}
else if (agt.indexOf("safari") > -1) {
    //alert("safari");
    document.write("<link rel='stylesheet' href='css/safari.css' type='text/css' media='screen' />");
}
else if (agt.indexOf("opera") > -1) {
    //alert("safari");
    document.write("<link rel='stylesheet' href='css/opera.css' type='text/css' media='screen' />");
}
else {
    //alert(agt);
    document.write("<link rel='stylesheet' href='css/moz.css' type='text/css' media='screen' />");
}