Markup:
<div id="menudiv">
    <section class="menusection">Level 1 XXX
            <nav class="submenu">
                <a href="xxx.php" title="Tooltip">Sub 1 XXX  1</a>
                <a href="xxx.php" title="Tooltip">Sub 1 XXX  2</a>
                <a href="xxx.php" title="Tooltip">Sub 1 XXX  3</a>
                <a href="xxx.php" title="Tooltip">Sub 1 XXX  4</a>
                <a href="xxx.php" title="Tooltip">Sub 1 XXX  5</a>
            </nav>
   </section>
    <section class="menusection">Level 1 YYY
            <nav class="submenu"> ... etc ...
        REPEAT for the number sections required
</div>    

CSS:
.menusection, .menusection2 {
                position:relative;
                width:15vw; 
                float:left;
                border:1px solid black; 
                z-index:10;
                height:1em;
                background-color:magenta;
                padding:3vh;
                border-radius:10px;
            }
.menusection:hover  {
                                    background-color:orange;
                                    transition-property:background-color;
                                    transition-duration:2s;
                                    transition-timing-function:ease-out;
                                }

http://coboldinosaur.com/pages/drop-down-menu.html

The first thing you might notice is that I am not using nested lists to layout the menu. That is an old XHTML layout technique. I am using the more semantically correct HTML5 <nav> tag. Menus are not lists, they are navigation so using the more modern tag makes sense, and it turns out to be easier to work with.

Drop down menu with fade in no scripting

css, html5

CSS