

    *{   
            padding: 0;   
            margin: 0;         
        }   
        ul{   
            list-style-type:none;   
        }   
        .triangle{   
        
            font-size: 1em;   
            color: white;    
        }   
        a{   
            text-decoration:none;   
            text-align: center;   
            font-weight: bold;   
        
        }   
        /*一级导航*/  
        ul.nav{   
            float: left;   
            border:1px solid gray;   
            margin-left: 10%;   
            margin-top:10px;   
            border-radius: 4px;   
            position: fixed;   
        }   
        ul.nav li{   
            float: left;   
            width: 9em;   
            background-color:yellowgreen;   
        }   
        ul.nav a{   
            display: block;   
            color: white;   
            line-height: 1.5em;   
            border-right: 1px solid white;   
            border-left: 1px solid white;   
            padding: 5px;   
        }   
        
        ul.nav a:hover,   
        ul.nav a:focus{   
            color: black;   
            background-color: #98FB98;   
            opacity: 0.5;   
        }   
        ul.nav li:first-child a{   
            border-left: 0;   
            border-bottom: 0;   
        }   
        ul.nav li:last-child a{   
            border-right: 0;   
            border-bottom: 0;   
        }   
        /*二级导航*/  
        ul.nav li ul{   
            width: 10em;           
            position: absolute;   
            left: -1000em;   
        }   
            
        ul.nav li:hover ul{   
            width: 10em;   
            left:auto;   
        }   
            
        ul.nav li ul a{   
            border-top: 1px solid white;   
            border-bottom: 1px solid white;   
            border-left: 0;   
            border-right: 0;   
                
        }   
        /*三级导航*/  
        ul.nav li:hover ul li ul{   
            width: 10em;   
            position: absolute;   
            left: -1000em;   
        
        }   
            
        ul.nav li:hover ul li:hover ul{   
            left: auto;   
            margin-left: 9.1em;   
            margin-top: -2.1em;   
        }   
        ul.nav li:hover ul li:hover ul.nav1{   
            left: auto;   
            margin-left: -9.1em;   
            margin-top: -2.1em;   
        }   

