如何居中基于CSS的下拉菜单？

lizardwizard 发表于 Dev

蜥蜴

我试图居中放置一个下拉列表，在屏幕上扩展灰色矩形，同时将文本保持在屏幕的正中央。目前应该只有三个项目。这些项目是家庭，作业和项目。

这是HTML

<HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
"http://www.w3.org/TR/html4/loose.dtd">
<html lang="en">
<head>
    <link type="text/css" rel="stylesheet" href="http://jamcgraw.iweb.bsu.edu/assignments/stylesheet.css" />
    <title>McGraw</title>
</head>
<div align="center">
<body>
        <li><a href="index.html">Home</a>
        </li>
        <li><a href="#">Assignments</a>
            <ul>
                <li>
               </li>                      
            </ul>
        </li>
        <li><a href="#">Projects</a>
            <ul>
                <li><a   href="http://jamcgraw.iweb.bsu.edu/projects/project1/project1.zip" target="_blank">
                    Project 1</a>
                </li>                       
            </ul>
        </li>
    </ul>
    <br />
    <br />   
    <h2>Some of my favorite websites include:<ul>
        <a href="http://facebook.com/">Facebook</a> </br>
        <a href="http://reddit.com/">Reddit</a> </br>
        <a href="http://twitch.tv/">Twitch.tv</a> </br>
        <a href="http://youtube.com/">Youtube</a> </br>
        <a href="http://noxxic.com/">Noxxic</a>
        </ul>
    </h2>    
</body>
</html>

以及DDM的.css

/*Begin Theme Style Code*/
/*Begin Regular Code*/
* {
margin: 0px;
}
/*End Regular Code*/
/*Begin Menu code*/
#menu-container ul,
#menu-container li,
#menu-container span,
#menu-container a {
margin: 0;
padding: 0;
position: relative;
}
#menu-container {
/* EDITED : ADD THE FOLLOWING LINE */  
text-align:center;


height: 49px;
border-radius: 0px 0px 0 0;
-moz-border-radius: 0px 0px 0 0;
-webkit-border-radius: 0px 0px 0 0;
background: #141414;

  background:url(data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAAxCAIAAACUDVRzAAAAA3NCSVQICAjb4U/gAAAALElEQVQImWMwMrJi+v//PxMDw3+m//8ZoPR/qBgDEhuXGLoeYswhXg8R5gAAdVpfoJ3dB5oAAAAASUVORK5CYII=) 100% 100%; 
background: -moz-linear-gradient(top, #32323a 0%, #141414 100%);
background: -webkit-gradient(linear, left top, left bottom, color-stop(0%, #32323a), color-stop(100%, #141414));
background: -webkit-linear-gradient(top, #32323a 0%, #141414 100%);
background: -o-linear-gradient(top, #32323a 0%, #141414 100%);
background: -ms-linear-gradient(top, #32323a 0%, #141414 100%);
background: linear-gradient(to bottom, #32323a 0%, #141414 100%);
border-bottom: 2px solid #0fa1e0;
}
 #menu-container:after,
 #menu-container ul:after {
 content: '';
 display: block;
 clear: both;
 }
 #menu-container a {
 background: #141414;
  background:url(data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAAxCAIAAACUDVRzAAAAA3NCSVQICAjb4U/gAAAALElEQVQImWMwMrJi+v//PxMDw3+m//8ZoPR/qBgDEhuXGLoeYswhXg8R5gAAdVpfoJ3dB5oAAAAASUVORK5CYII=) 100% 100%; 
  background: -moz-linear-gradient(top, #32323a 0%, #141414 100%);
  background: -webkit-gradient(linear, left top, left bottom, color-stop(0%, #32323a), color-stop(100%, #141414));
  background: -webkit-linear-gradient(top, #32323a 0%, #141414 100%);
  background: -o-linear-gradient(top, #32323a 0%, #141414 100%);
  background: -ms-linear-gradient(top, #32323a 0%, #141414 100%);
  background: linear-gradient(to bottom, #32323a 0%, #141414 100%);
  color: #ffffff;
  display: inline-block;
  font-family: Helvetica, Arial, Verdana, sans-serif;
  font-size: 12px;
  line-height: 49px;
  padding: 0 20px;
  text-decoration: none;
  }
  #menu-container ul {
  list-style: none;
  }
  #menu-container > ul {
  }
  #menu-container > ul > li {
  /*EDITED : CHANGE THE FOLLOWING LINE*/
  float: left;
  }
  #menu-container > ul > li:hover:after {
  content: '';
  display: block;
  width: 0;
  height: 0;
  position: absolute;
  left: 50%;
  bottom: 0;
  border-left: 10px solid transparent;
  border-right: 10px solid transparent;
  border-bottom: 10px solid #0fa1e0;
  margin-left: -10px;
  }
#menu-container > ul > li:first-child > a {
border-radius: 0px 0 0 0;
-moz-border-radius: 0px 0 0 0;
-webkit-border-radius: 0px 0 0 0;
}
#menu-container > ul > li:last-child > a {
border-radius: 0 0px 0 0;
-moz-border-radius: 0 0px 0 0;
-webkit-border-radius: 0 0px 0 0;
 }
 #menu-container > ul > li.active > a {
 box-shadow: inset 0 0 3px #000000;
-moz-box-shadow: inset 0 0 3px #000000;
-webkit-box-shadow: inset 0 0 3px #000000;
 background: #070707;      background:url(data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAAxCAIAAACUDVRzAAAAA3NCSVQICAjb4U/gAAAALklEQVQImWNQU9Nh+v//PxMDw3+m//8ZkNj/mRgYIHxy5f//Z0BSi18e2TwS5QG4MGB54HL+mAAAAABJRU5ErkJggg==) 100% 100%; 
background: -moz-linear-gradient(top, #26262c 0%, #070707 100%);
background: -webkit-gradient(linear, left top, left bottom, color-stop(0%, #26262c), color-stop(100%, #070707));
background: -webkit-linear-gradient(top, #26262c 0%, #070707 100%);
background: -o-linear-gradient(top, #26262c 0%, #070707 100%);
background: -ms-linear-gradient(top, #26262c 0%, #070707 100%);
background: linear-gradient(to bottom, #26262c 0%, #070707 100%);
}
#menu-container > ul > li:hover > a {
background: #070707;
  background:url(data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAAxCAIAAACUDVRzAAAAA3NCSVQICAjb4U/gAAAALklEQVQImWNQU9Nh+v//PxMDw3+m//8ZkNj/mRgYIHxy5f//Z0BSi18e2TwS5QG4MGB54HL+mAAAAABJRU5ErkJggg==) 100% 100%; 
 background: -moz-linear-gradient(top, #26262c 0%, #070707 100%);
 background: -webkit-gradient(linear, left top, left bottom, color-stop(0%, #26262c), color-stop(100%, #070707));
 background: -webkit-linear-gradient(top, #26262c 0%, #070707 100%);
 background: -o-linear-gradient(top, #26262c 0%, #070707 100%);
 background: -ms-linear-gradient(top, #26262c 0%, #070707 100%);
 background: linear-gradient(to bottom, #26262c 0%, #070707 100%);
 box-shadow: inset 0 0 3px #000000;
 -moz-box-shadow: inset 0 0 3px #000000;
 -webkit-box-shadow: inset 0 0 3px #000000;
 }
#menu-container .has-sub {
z-index: 1;
}
#menu-container .has-sub:hover > ul {
display: block;
}
#menu-container .has-sub ul {
display: none;
position: absolute;
width: 200px;
top: 100%;
left: 0;
}
#menu-container .has-sub ul li {
*margin-bottom: -1px;
}
#menu-container .has-sub ul li a {
background: #0fa1e0;
border-bottom: 1px dotted #6fc7ec;
filter: none;
font-size: 11px;
display: block;
line-height: 120%;
padding: 10px;
}
#menu-container .has-sub ul li:hover a {
background: #0c7fb0;
}
#menu-container .has-sub .has-sub:hover > ul {
display: block;
}
#menu-container .has-sub .has-sub ul {
display: none;
position: absolute;
left: 100%;
top: 0;
}
#menu-container .has-sub .has-sub ul li a {
background: #0c7fb0;
border-bottom: 1px dotted #6db2d0;
}
#menu-container .has-sub .has-sub ul li a:hover {
background: #095c80;
}
#menu-container {
-moz-box-shadow: 0 0 10px #888;
-webkit-box-shadow: 0 0 10px #888;
box-shadow: 0 0 10px #888;
}
/*End Menu Code*/
/*Begin Button Code*/
button.button {
border: 0 none;
font-size: 16px;
font-weight: 600;
height: 34px;
line-height: 22px;
margin-bottom: 5px;
margin-left: 0;
margin-right: 1px;
padding: 4px 11px 10px;
color: #FFFFFF;
background-color: #00CCFF;
font-family: Segoe UI, Tahoma, Helvetica, sans-serif;
}

button.button:hover {
background-color:#24459A
}
/*End Button Code*/
/*Begin Table Logo Code*/
table.header {
width: 100%;
border-collapse: collapse;
border: none;
}

table.header td {
vertical-align: top;
border: 1px solid #BFBFBF;
padding: -1px;
}

table.header td.center {
width: 800px;
height: 600px;
}
img.logo {
display: block;
margin-left: auto;
margin-right: auto;
}
/*End Table Logo Code*/
/*End Theme Style Code*/