This question seems crazy, but I wanted to clearly explain everything.

Desired Result

I have a horizontal panel with a submenu. I created it from scratch, so I do not use any existing frameworks. It uses a combination of buttons, anchors, and spaces for semantic markup.

• bindings for elements that go to a new page
• for items that don't go anywhere but have a submenu
• covers disabled items

Note. This site is intended for a limited number of specific users, so I am not worried about the lack of accessibility.

The submenu should be as wide as the widest menu item that it contains. And each menu item should fill the width of the submenu so that the default cursor and focus are displayed.

Problem

In Firefox, a submenu does not expand to the width of the widest element in the following scenario:

• Submenu
• absolutely positioned Submenu
• contained inside a block that has a position other than static
• The longest menu item is a button

I tested with Chrome, IE 8, Firefox 12, and Firefox 20. It displays as desired in Chrome and IE, but not in any version of Firefox.

I created a smaller version with JavaScript, images, disabled items, and many deleted menu items. The code is below as well as on jsFiddle . Here is a screenshot in Firefox 20.

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HTML (jsFiddle)

<ul id="navAdminMenu">
    <li><a href="#">Companies</a></li
    ><li class="hasSubmenu"><button type="button">Books</button>
        <ul>
            <li><a href="#">Manage Books</a></li
            ><li><a href="#">PDF Profiles</a></li
            ><li class="hasSubmenu"><button type="button">Customize PDF Titles</button>
                <ul>
                    <li><a href="#">Page Titles</a></li
                    ><li class="hasSubmenu"><button type="button">Section Titles</button>
                        <ul>
                            <li><a href="#">Profile Section</a></li
                            ><li><a href="#">Index Section</a></li>
                        </ul>
                    </li>
                </ul>
            </li>
        </ul>
    </li
    ><li class="hasSubmenu"><button type="button">Lists</button>
        <ul>
            <li class="hasSubmenu"><button type="button">Categories</button>
                <ul>
                    <li><a href="#">Manage</a></li
                    ><li><a href="#">Reports</a></li>
                </ul>
            </li
            ><li><a href="#">Key Contact Positions</a></li>
        </ul>
    </li>
</ul>

CSS

#navAdminMenu {
    font-family: Arial, Helvetica, sans-serif;
    font-size: 1em;
    list-style: none;
    margin: 0;
    padding: 0;
    background-color: #efefef;
}
#navAdminMenu button {
    margin: 0;
    padding: 0;
    vertical-align: baseline;
    border: none;
    background-color: transparent;
    cursor: pointer;
    font-family: Arial, Helvetica, sans-serif;
    font-size: 1em;
}
#navAdminMenu button::-moz-focus-inner {
    padding: 0;
    border: none;
}
#navAdminMenu a {
    text-decoration: none;
}
#navAdminMenu li {
    display: inline-block;
    margin: 0;
    border-right: 1px solid #ccc;
}
#navAdminMenu li:hover {
    background-color: #4b545f;
}
#navAdminMenu > li > button, #navAdminMenu > li > a {
    display: inline-block;
    height: 2.3em;
    line-height: 2.6;
    padding: 0 10px;
}
#navAdminMenu > li > button, #navAdminMenu > li > a {
    color: #06c;
}
#navAdminMenu > li > button:focus, #navAdminMenu > li > a:focus {
    outline: 0; /* Firefox displays outline outside the menu box-shadow */
    box-shadow: 0 0 0 3px #06c;
}
#navAdminMenu > li:hover > button, #navAdminMenu > li:hover > a {
    color: #fff;
}
#navAdminMenu > li.hasSubmenu > button:after {
    content: "v";
    display: inline-block;
    width: 13px;
    margin-left: 5px;
}
#navAdminMenu ul {
    display: none;
    position: absolute;
    padding: 0;
    background-color: #5f6975;
}
#navAdminMenu li:hover > ul {
    display: block;
}
#navAdminMenu ul > li {
    display: block;
    position: relative;
    border-top: 1px solid #999;
    border-bottom: 1px solid #000;
}
#navAdminMenu ul > li > button, #navAdminMenu ul > li > a {
    height: 2em;
    line-height: 2;
    padding: 0 30px 0 10px;
    white-space: nowrap;
}
#navAdminMenu ul > li > button {
    width: 100%; /* full width of submenu */
    text-align: left;
}
#navAdminMenu ul > li > a {
    display: block; /* full width of submenu */
}
#navAdminMenu ul > li > button, #navAdminMenu ul > li > a {
    color: #fff;
}
#navAdminMenu ul > li > button:focus, #navAdminMenu ul > li > a:focus {
    outline: #fdcb01 solid 3px;
}
#navAdminMenu ul > li.hasSubmenu > button:after {
    content: ">";
    width: 16px;
    position: absolute;
    right: 0;
}
#navAdminMenu ul ul {
    left: 100%;
    top: 0;
}

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