var exp = new Date();                                   
exp.setTime(exp.getTime() + (1000 * 60 * 60 * 24 * 31)); 

if (document.all) {
	setCookie("browser","IE", exp);
}
else if (document.layers) {
	setCookie("browser","NN", exp);
}
else {
	setCookie("browser","UNKNOWN", exp);
}