Menu che scorre insieme alla pagina

      <script type="text/javascript">
            $(document).ready(function () {
                var yOffset = $("div#menu").offset().top;
                $(window).scroll(function () {
                    if ($(window).scrollTop() > yOffset) {
                        $("div#menu").css({
                            'width': $(".d960").width() * 0.3,
                            'top': 0,
                            'left': $("div#menu").offset().left,
                            'right': $("div#menu").offset().right,
                            'position': 'fixed',
                            
                        });
                    } else {
                        $("#menu").css({
                            'width': "100%",
                            'top': yOffset + 'px',
                            'left': 0,
                            'right': 0,
                            'position': 'static'
                        });
                    }
                });
            });
        </script>




<div id="menu" style="z-index:999; float:left; ">

   <div id="nav">
      
        <ul>
			<li>
				<a href="#"><?php echo $labels['l_menu_immobili']?></a>
					<ul class="fallback">
						   <li><a href="<?php echo $_SESSION["www"]["lang"] ?>/products/287/commerciale"><?php echo $labels['l_menu_commerciale']?></a></li>
						   <li><a href="<?php echo $_SESSION["www"]["lang"] ?>/products/288/industriale"><?php echo $labels['l_menu_industriale']?></a></li>
						   <li><a href="<?php echo $_SESSION["www"]["lang"] ?>/products/360/residenziale"><?php echo $labels['l_menu_residenziale']?></a></li>
						   <li><a href="<?php echo $_SESSION["www"]["lang"] ?>/products/369/terreni"><?php echo $labels['l_menu_terreni']?></a>

//resto del codice...