HTML/CSS 子子菜单

Question

我在将子子菜单放入我 html/css 设计的菜单时遇到问题。我附上了一张我从给定代码中得到的结果图片。如果有人能指出我在哪里犯了错误，将不胜感激。我已经看了所有内容 2 遍，感觉我只是错误地实施了 css。

#topbar {
background-color: #222;
}

#topbar_wrapper {
width: 100%;
margin: 0 auto;
text-align: left;
}

#mainmenu {
list-style-type: none;
padding: 0px;
margin: 0px;
position: relative;
min-width: 200px;
}
#mainmenu li {
display: inline-block;
width: 200px;
}
#mainmenu li:hover {
background-color: #333;
}
#mainmenu li a{
color: #CCC;
display: block;
padding: 15px;
text-decoration: none;
}
#mainmenu li:hover ul {
display: block;
}

#sortmenu {
display: none;
position: absolute;
background-color: #333;
border: 5px solid #222;
border-top: 0;
margin-left: -5px;
}
#sortmenu li {
display: block;
}
#sortmenu li a:hover {
color: #699;
}
#sortmenu li: hover ul {
display: inline-block;
}

#sortsongmenu {
display: in-line;
position: relative;
background-color: #333;
border: 5px solid #222;
border-left: 0;
margin-left: -5px;
}

#sortsongmenu li{
display: inline-block;
}

#sortsongmenu li a:hover {
color: #DB7093;
}

<div id="topbar">
    <div id="topbar_wrapper">
        <ul id="mainmenu">
            <li><a href="#">Home</a></li><li>
            <a href="#">Search</a></li><li>
            <a href="#">Sort By &#9660</a>
                <ul id="sortmenu">
                    <li><a href='#'>Song</a>
                        <ul id="sortsongmenu">
                            <li><a href='#'>A to Z</a></li><li>
                            <a href='#'>Z to A</a></li>
                        </ul>
                    </li><li>   
                    <a href='#'>Artist</a></li><li>
                    <a href='#'>Album</a></li><li>
                    <a href='#'>Genre</a></li><li>
                    <a href='#'>BPM</a></li><li>
                    <a href='#'>Release Date</a></li>
                </ul>
            </li><li>
            <a href="#">Add Song</a></li><li>
            <a href="#">Contant Us</a></li>
        </ul>
    </div>
</div>

Answer 1

#sortmenu li: hover ul

需要：

#sortmenu li:hover ul

也在#sortsongmenu

下

display: in-line;

需要

display: none;

HTML/CSS 子子菜单

HTML/CSS sub-submenu

html

css

html-lists

submenu