if(navigator.userAgent.indexOf("MSIE 5") > 0)
{
        document.write('<LINK media="all" href="/css/ie5.css" type="text/css" rel="stylesheet" />');
}

if(navigator.userAgent.indexOf("Netscape") > 0)
{
        document.write('<LINK media="all" href="/css/netscape.css" type="text/css" rel="stylesheet" />');
}

if(navigator.userAgent.indexOf("Gecko") > 0)
{
        document.write('<LINK media="all" href="/css/gecko.css" type="text/css" rel="stylesheet" />');
}

if(navigator.userAgent.indexOf("Opera") > 0)
{
        document.write('<LINK media="all" href="/css/opera.css" type="text/css" rel="stylesheet" />');
}