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<head><meta charset&＃61;"UTF-8"><title>置顶菜单title><script type&＃61;"text/Javascript" src&＃61;"js/jquery-1.12.4.min.js">script><script type&＃61;"text/Javascript">$(function(){$(window).scroll(function() {var nowTop &＃61; $(document).scrollTop();if(nowTop>200){$(&＃39;.menu&＃39;).css({position:&＃39;fixed&＃39;,left:&＃39;50%&＃39;,top:0,marginLeft:-480});$(&＃39;.menu_pos&＃39;).show();}else{$(&＃39;.menu&＃39;).css({position:&＃39;static&＃39;, marginLeft:&＃39;auto&＃39;});$(&＃39;.menu_pos&＃39;).hide();}if(nowTop>400){$(&＃39;.totop&＃39;).fadeIn();}else{$(&＃39;.totop&＃39;).fadeOut();}});$(&＃39;.totop&＃39;).click(function() {$(&＃39;html,body&＃39;).animate({&＃39;scrollTop&＃39;:0});});})script><style type&＃61;"text/css">body{margin:0px;}.logo_bar{width:960px;height:200px;background-color:#f0f0f0;margin:0 auto;}.menu,.menu_pos{width:960px;height:50px;margin:0 auto;background-color:gold;text-align:center;line-height:50px;}.menu_pos{display:none;}.down_con{width:960px;height:1800px;margin:0 auto;}.down_con p{margin-top:100px;text-align:center;}.totop{width:50px;height:50px;background:url(images/up.png) center center no-repeat #000;border-radius:50%;position:fixed;right:50px;bottom:50px;display:none;}style>head>
<body><div class&＃61;"logo_bar">顶部logodiv><div class&＃61;"menu">置顶菜单div><div class&＃61;"menu_pos">div><div class&＃61;"down_con"><p style&＃61;"color:red">网站主内容p><p>网站主内容p><p>网站主内容p><p>网站主内容p><p>网站主内容p>div><a href&＃61;"Javascript:;" class&＃61;"totop">a>
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效果图&＃xff1a;
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