JQuery 树下下拉菜单

.st_tree{ 
    padding:10px;
}

.st_tree a{ 
    color:#222; 
    text-decoration:none; 
}

.st_tree a:hover{ 
    /* color:#f33; */
    color:Green;
    
    text-decoration:underline;
}

.st_tree ul{ 
    padding:0 0 0 18px; 
    margin:0; 
}

.st_tree ul li{ 
    font-size:13px; 
    color:#222; 
    line-height:18px; 
    cursor:pointer;
    list-style:none; 
    background:url(../Images/st_node.gif); /*文件*/
    background-repeat:no-repeat; 
    padding:0 0 3px 20px;
}


.st_tree .folder{ 
    list-style-image:url(../Images/st_icon.png); /*向右的箭头*/
    background:url(../Images/st_folder.gif); /* 文件夹图片  */
    background-repeat:no-repeat; 
    padding:0 0 0 20px; 
}

.st_tree .open{ 
    list-style-image:url(../Images/st_icon_open.png); /*向下的箭头 打开的*/
    background:url(../Images/st_folder_open.gif); /* 打开的文件夹*/
    background-repeat:no-repeat; 
    padding:0 0 0 20px; 
}

.st_tree .hover{
    background-color:#ffa;
}