HTML 中让DIV不随滚动条滚动，使终显示在浏览器的固定位置

<script type="text/javascript" src="js/jquery.min.js"></script>
<script>
$.fn.smartFloat = function() {
var position = function(element) {
var top = element.position().top, pos = element.css("position");
var browser=navigator.appName;
var browser2=navigator.userAgent;
$(window).scroll(function() {
var scrolls = $(this).scrollTop();
if (scrolls > 120) {
if (window.XMLHttpRequest) {
if(browser2.indexOf("Chrome") > -1 || browser2.indexOf("MSIE")> -1 || browser2.indexOf("iPhone")> -1){
element.css({position: "fixed",top: 0});//更改这里的0可以设定在哪个Y位置固定
}else{
element.css({position: "fixed",top: scrolls});
}
} else {
element.css({top: scrolls});
}
}else {
element.css({position: pos,top: top});
}
});
};
return $(this).each(function() {
position($(this));
});
};

$("#first").smartFloat();
</script>