$(document).ready(function(){
	var OSName="Unknown OS";
	if (navigator.appVersion.indexOf("Win")!=-1) OSName="Windows";
	if (navigator.appVersion.indexOf("Mac")!=-1) OSName="MacOS"; //document.getElementById('main_menu').style.display = 'none'; document.getElementById('main_menu_mac').style.display = 'block';
	if (navigator.appVersion.indexOf("X11")!=-1) OSName="UNIX";
	if (navigator.appVersion.indexOf("Linux")!=-1) OSName="Linux";

	//document.write('Ваша ОС: '+OSName);
});