爲什麽我按照代碼來 小箭頭什麽都沒出現
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<title>无标题文档</title>
<style type="text/css">
.nav {
width: 960px;
margin: 60px auto;
border: 1 solid #222;
background-color: #111;
background-image: linear-gradient(#444, #111);
border-radius: 6px;
box-shadow: 0 1px 1px #777;
padding: 0;
list-style: none;
font-family: "微软雅黑";
}
.nav:before,
.nav:after {
content: '';
display: table;
}
.nav:after {
clear: both;
}
.nav li {
float: left;
border-right: 1px solid #222;
box-shadow: 1px 0 0 #444;
position: relative;
}
.nav li a {
float: left;
padding: 12px 30px;
text-decoration: none;
font: bold 12px;
color: #999;
text-shadow: 0 1px 0 #000;
}
.nav li a:hover {
color: #fafafa;
}
.nav li ul {
visibility: hidden;
position: absolute;
list-style: none;
top: 38px;
left: 0;
z-index: 1;
padding: 0;
background-color: #444;
background-image: linear-gradient(#444, #111);
box-shadow: 0 -1 0 rgba(255, 255, 255, .3);
border-radius: 3px;
opacity: 0;
/*透明度*/
margin: 20px 0 0 0;
transition: all .2s ease-in-out;
/*transition配合hover使用*/
}
.nav li:hover>ul {
/*>选择子一级的ul*/
opacity: 1;
visibility: visible;
/*元素可见*/
margin: 0;
}
;
.nav ul li {
float: none;
display: block;
border: 0;
box-shadow: 0 1px 0 #111, 0 2px 0 #666;
}
.nav ul a {
padding: 10px;
width: 130px;
display: block;
float: none;
}
.nav ul a:hover {
background-color: #0186ba;
background-image: linear-gradient(#04acec, #0186ba);
}
.nav ul li:first-child > a {
border-radius: 3px 3px 0 0;
}
.nav ul li:last-child > a {
border-radius: 0 0 3px 3px;
}
.nav ul li:first-child > a:before {
content: '';
position: absolute;
left: 40px;
top: -6px;
border-left: 6px solid transparent;
border-right: 6px solid transparent;
border-bottom: 6px solid #444;
}
.nav ul li:first-child > a:hover:before {
border-bottom-color: #04acec;
}
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