Focusin和focusout方法无法在firefox中运行

I have a list like this:

我有一个这样的列表:

<ul class="tabs-dropdown">
    <li><a href="/go.html?url=/home">Home</a></li>

    <li>
        <a href="/go.html?url=javascript:">French Alps</a>
        <div>
            <ul>
                <li><a href="/go.html?url=/region/french-alps/about">About</a></li>
                <li><a href="/go.html?url=/region/french-alps/properties">Properties</a></li>
            </ul>
        </div>
    </li>

    <li>
        <a href="/go.html?url=javascript:">Swiss Alps</a>
        <div>
            <ul>
                <li><a href="/go.html?url=/region/swiss-alps/about">About</a></li>
                <li><a href="/go.html?url=/region/swiss-alps/properties">Properties</a></li>
            </ul>
        </div>
    </li>

    <li><a href="/go.html?url=/finance">Finance</a></li>
    <li><a href="/go.html?url=/contact">Contact Us</a></li>
</ul>
<ul cla