I am learning HTML and CSS at the moment. I have my navigation menu done, but I have submenus under the main selections. Here is my code:

```
#navigation ul {
    font-family:Arial;
    list-style-type:none;
    margin:0;
    padding:0;
}
#navigation li {
    font-family:Arial;
    font-size:11px;
    display:inline;
    float:left;
    background-color:#FFF;
}
#navigation a {
    display:block;
    width:60px;
    background-color:#FFF;
}

```

And here is my HTML (I am making a site on Half Life and Portal to learn):

```
<div id="menus">
    <div id="navigation">
        <ul>
            <li><a href="#">Aperture Science</a></li>
            <ul>
                <li><a href="#">GLaDOS</a></li>
                <li><a href="#">Testing Chambers</a></li>
                <li><a href="#">The Player (Chell)</a></li>
            </ul>
        </ul>
        <ul>
            <li>Black Mesa</li>
            <ul>
                <li>The Combine</li>
                <li>The Resistance</li>
                <li>The Player (Gordon Freeman)</li>
            </ul>
        </ul>
</div>

```

What do I need to change?

Note: Yes, I haven't finished putting in quick 'a' tags...