Change CSS on scroll
var scroll_pos = 0;
$(document).scroll(function() {
scroll_pos = $(this).scrollTop();
if(scroll_pos > 210) {
$(".navbar-default").css({"background-color": "black" , "padding-top" : 0});
} else {
$(".navbar-default").css({"background-color" : "transparent" , "padding-top" : "30px"});
}
});