window.onscroll = function () {
    var scrollTop = document.documentElement.scrollTop
    if (navigator.userAgent.toLowerCase().indexOf('chrome') > -1) {
		scrollTop = document.body.scrollTop;
    }
if(scrollTop>180){
	$('.menu').css( "position", "absolute" );
	$('.menu').css( "top", (scrollTop)+'px' );
}else{ 
		$('.menu').css( "position", "relative" );
		$('.menu').css( "top", 0+'px' );
		}

}