var agt = navigator.userAgent.toLowerCase();
var is_major = parseInt(navigator.appVersion);
var is_ie = ((agt.indexOf('msie') != -1) && (agt.indexOf('opera') == -1));
var is_nav = ((agt.indexOf('mozilla') != -1) && (agt.indexOf('spoofer') == -1)
	&& (agt.indexOf('compatible') == -1) && (agt.indexOf('opera') == -1)
	&& (agt.indexOf('webtv') == -1) && (agt.indexOf('hotjava') == -1));

var is_ie3 = (is_ie && (is_major < 4));
var is_ie4 = (is_ie && (is_major == 4) && (agt.indexOf('msie 4') != -1));
var is_ie4up = (is_ie && (is_major >= 4));
var is_ie5up = (is_ie && !is_ie3 && !is_ie4);

var is_mac = (agt.indexOf('mac') != -1);

if(!is_mac && is_nav && (is_major <= 4)) {
	document.write("<link rel=\"stylesheet\" href=\"http://www.perioletter.com/css/win_other.css\" type=\"text/css\">");
} else if(is_mac && is_nav) {
	document.write("<link rel=\"stylesheet\" href=\"http://www.perioletter.com/css/mac_netscape.css\" type=\"text/css\">");
} else {
	document.write("<link rel=\"stylesheet\" href=\"http://www.perioletter.com/css/all_iexplorer.css\" type=\"text/css\">");
}