为什么nav_left ,nav_mid, nav_right不在一行？
<!DOCTYPE html> <html> <head> <title></title> <link rel="stylesheet" type="text/css" href="css/main.css"> <script type="text/javascript" src="js/setHomeSetFav.js" charset="gb2312"></script> </head> <body> <div class="top"> <div class="top_content"> <ul> <li><a href="#">联系我们</a></li> <li><a href="#" onclick="AddFavorite(window.location,document.title)">加入收藏</a></li> <li><a href="#" onclick="SetHome(window.location)">设为首页</a></li> </ul> </div> </div> <!--top结束--> <div class="wrap"> <div class="logo"> <div class="logo_left"> <img src="images/logo.jpg" alt="慕课网"/> </div> <div class="logo_right"> <img src="images/tel.jpg" alt="服务热线"/>24小时服务热线：<span class="tel"> 123-456-7890</span> </div> </div><!--logo结束--> <div class="nav"> <div class="nav_left"></div> <div class="nav_mid"> <div class="nav_mid_left"> <ul> <li><a href="#">首页</a></li> <li><a href="list.html">关于慕课</a></li> <li><a href="list.html">新闻动态</a></li> <li><a href="list.html">课程中心</a></li> <li><a href="list.html">在线课程</a></li> <li><a href="list.html">人才招聘</a></li> </ul> </div> <div class="nav_mid_right"> <form action="" method="post"> <input type="text" /> </form> </div> </div> <div class="nav_right"></div> </div><!--nav结束--> </div><!--wrap结束--> </body> </html>
*{
margin: 0;
padding: 0;
font-size: 12px;
}
body{
background-color: #f5f5f5;
}
.top{
width: 100%;
height: 27px;
background: url(../images/top_bg.jpg) repeat-x;
}
.top_content{
width: 1000px;
margin: 0 auto;
}
.top_content li{
list-style-image: url(../images/li_bg.gif);
float: right;
width: 70px;
line-height: 27px;
}
.top_content li:link, .top_content li:visited{
color: #8e8e8e;
text-decoration: none;
}
.top_content li:hover, .top_content li:active{
color:#900;
text-decoration: none;
}
.wrap{
width: 1000px;
margin: 0 auto;
}
.logo{
height: 80px;
background-color: #fff;
}
.logo_left{
width: 200px;
float: left;
}
.logo_right{
width: 300px;
float: right;
height: 28px;
margin-top: 30px;
color: #8e8e8e;
}
.logo_right img{
vertical-align: middle;
margin-right: 10px;
}
.tel{
font-family: "微软雅黑";
font-size: 16px
color: #c00;
}
.nav{
height: 40px;
}
.nav_left{
width: 10px;
background: url(../images/nav_left.jpg) no-repeat;
}
.nav_mid{
width: 980px;
background: url(../images/nav_bg.jpg) repeat-x;
}
.nav_right{
width: 10px;
background: url(../images/nav_right.jpg) no-repeat;
}
.nav_left,.nav_mid,.nav_right{
float: left;
height: 40px;
}
