var agt=navigator.userAgent.toLowerCase();
if (agt.indexOf("ie 6") > -1 )
{
    document.write("<link rel='stylesheet' href='style/IE6.css' type='text/css' media='screen' />"); 
    document.write("<link rel='stylesheet' href='style/IEMenu6.css' type='text/css' media='screen' />"); 
}
else if (agt.indexOf("ie 7") > -1 || agt.indexOf("ie 8") > -1)
{
    document.write("<link rel='stylesheet' href='style/IE7.css' type='text/css' media='screen' />"); 
}

else if (agt.indexOf("opera") > -1) {
    document.write("<link rel='stylesheet' href='style/Opera.css' type='text/css' media='screen' />");
}  

else if (agt.indexOf("firefox") > -1) {
    document.write("<link rel='stylesheet' href='style/moz.css' type='text/css' media='screen' />");
}

else if (agt.indexOf("chrome") > -1) {
    document.write("<link rel='stylesheet' href='style/chrome.css' type='text/css' media='screen' />");
}