//获取选中的下拉框
$('#someElement').find('option:selected');
$('#someElement option:selected');

//返回头部滑动动画

<script type="text/javascript">
$(function () {
jQuery.fn.scroll = function (speed) {
var target = $(this).offset().top;
$('html,body').stop().animate({ scrollTop: target }, speed);
return this;

}

$("#goheader").click(function () {
$("body").scroll(500);
return false;
})
})
</script>

<div id="Div1" style=" background-color:#f00; width:100px; height:3000px; ">

</div>

<input id="goheader" type="button" value="返回头部" />