Next() Not Picking Up An Inner UL With "display: None" In IE7

This is happening with the following markup:

• Test

Then, to access the <ul> you are far better using .find so it would be $("li").find("ul") as this will access the <ul> inside the <li> only.

<ul id="sideMenu" class="menuFontStyle">
    <li class="category">Test
        <ul class="secondLevel" style="display: none;">
            <li></li>
        </ul>
    </li>
</ul>

Solution 2:

That is invalid HTML, so you shouldn't be surprised at bizarre results. ul elements may not have other ul elements as direct children; they may only contain li elements. IE7 presumably wraps the ul in another li or something similar to make it valid.

Make your HTML valid: this will help browsers to transform it into the DOM structure that you intend and your JS coding will be a lot easier.