Fixed block while scroll page

scripts.js

//Фиксируем форму обратной связи
		var	$section_of_form = $("#fixed_scroll_form").closest('section'),
			fixed_scroll_form = $section_of_form.offset().top - 50;
		//Выставляем текущую ширину
		$section_of_form.css('width', $section_of_form.css('width'));
		$(window).bind("scroll", function() {
		    var offset = $(this).scrollTop();

		    if (offset >= fixed_scroll_form && !$section_of_form.hasClass("fixed_scroll_form")) {
		        $section_of_form.addClass('fixed_scroll_form');
		    } else if (offset < fixed_scroll_form) {
		        $section_of_form.removeClass('fixed_scroll_form');
		    }
		});