Here is my example HTML.

And I want to have scroll for my LI items.

Which are of 2 levels. Means, I want to apply class on every UL.

So how can I do that. By using JQuery or CSS tweaking.

PS: I am using this example.

<ul id="nav" class="dropdown">
<li class="dir">
    Item_Root
    <ul>
        <li class="dir">
            Item_1_Level
            <ul>
                <li>Item_Level_2</li>
                <li>Item_Level_2</li>
                <li>Item_Level_2</li>
                <li>.... up to N items</li>
            </ul>
        </li>
        <li>Item_Level_1</li>
        <li>Item_Level_1</li>
        <li>Item_Level_1</li>
        <li>Item_Level_1</li>
        <li>.... up to N items</li>
    </ul>
</li>

 </ul>