jQuery置顶特效，直接引用即可

window.onload = function() {
	demoload();
};

var demoload = function() {
	// document.getElementById("datehour").style.display="none";

	var scrolltotop = {
		// startline: Integer. Number of pixels from top of doc scrollbar is
		// scrolled before showing control
		// scrollto: Keyword (Integer, or "Scroll_to_Element_ID"). How far to
		// scroll document up when control is clicked on (0=top).
		setting : {
			startline : 100,
			scrollto : 0,
			scrollduration : 1000,
			fadeduration : [500, 100]
		},
		controlHTML : '<img src="images/top.gif" style="width:53px;height:53px" />', // HTML
		// for
		// control,
		// which
		// is
		// auto
		// wrapped
		// in
		// DIV
		// w/
		// ID="topcontrol"
		controlattrs : {
			offsetx : 5,
			offsety : 0
		}, // offset of control relative to right/ bottom of window corner
		anchorkeyword : '#top', // Enter href value of HTML anchors on the page
		// that should also act as "Scroll Up" links
		state : {
			isvisible : false,
			shouldvisible : false
		},

		scrollup : function() {
			if (!this.cssfixedsupport) // if control is positioned using
				// JavaScript
				this.$control.css({
							opacity : 0
						}) // hide control immediately after clicking it
			var dest = isNaN(this.setting.scrollto)
					? this.setting.scrollto
					: parseInt(this.setting.scrollto)
			if (typeof dest == "string" && jQuery('#' + dest).length == 1) // check
				// element
				// set
				// by
				// string
				// exists
				dest = jQuery('#' + dest).offset().top
			else
				dest = 0
			this.$body.animate({
						scrollTop : dest
					}, this.setting.scrollduration);
		},

		keepfixed : function() {
			var $window = jQuery(window)
			var controlx = $window.scrollLeft() + $window.width()
					- this.$control.width() - this.controlattrs.offsetx
			var controly = $window.scrollTop() + $window.height()
					- this.$control.height() - this.controlattrs.offsety
			this.$control.css({
						left : controlx + 'px',
						top : controly + 'px'
					})
		},

		togglecontrol : function() {
			var scrolltop = jQuery(window).scrollTop()
			if (!this.cssfixedsupport)
				this.keepfixed()
			this.state.shouldvisible = (scrolltop >= this.setting.startline)
					? true
					: false
			if (this.state.shouldvisible && !this.state.isvisible) {
				this.$control.stop().animate({
							opacity : 1
						}, this.setting.fadeduration[0])
				this.state.isvisible = true
			} else if (this.state.shouldvisible == false
					&& this.state.isvisible) {
				this.$control.stop().animate({
							opacity : 0
						}, this.setting.fadeduration[1])
				this.state.isvisible = false
			}
		},

		init : function() {
			jQuery(document).ready(function($) {
				var mainobj = scrolltotop
				var iebrws = document.all
				mainobj.cssfixedsupport = !iebrws || iebrws
						&& document.compatMode == "CSS1Compat"
						&& window.XMLHttpRequest // not IE or IE7+ browsers
				// in standards mode
				mainobj.$body = (window.opera)
						? (document.compatMode == "CSS1Compat"
								? $('html')
								: $('body'))
						: $('html,body')
				mainobj.$control = $('<div id="topcontrol">'
						+ mainobj.controlHTML + '</div>').css({
							position : mainobj.cssfixedsupport
									? 'fixed'
									: 'absolute',
							bottom : mainobj.controlattrs.offsety,
							right : mainobj.controlattrs.offsetx,
							opacity : 0,
							cursor : 'pointer'
						}).attr({
							title : '返回顶部'
						}).click(function() {
							mainobj.scrollup();
							return false
						}).appendTo('body')
				if (document.all && !window.XMLHttpRequest
						&& mainobj.$control.text() != '') // loose check for
					// IE6 and below,
					// plus whether
					// control contains
					// any text
					mainobj.$control.css({
								width : mainobj.$control.width()
							}) // IE6- seems to require an explicit width on a
				// DIV containing text
				mainobj.togglecontrol()
				$('a[href="' + mainobj.anchorkeyword + '"]').click(function() {
							mainobj.scrollup()
							return false
						})
				$(window).bind('scroll resize', function(e) {
							mainobj.togglecontrol()
						})
			})
		}
	}
	scrolltotop.init()

}