There are a couple of ways that you can accomplish this. You can do the following:
<li>
@Html.ActionLink("Clients", "Index", "User", new { @class = "elements" }, null)
</li>
or this:
<li>
<a href="@Url.Action("Index", "Users")" class="elements">
<span>Clients</span>
</a>
</li>
Lately I do the following:
<a href="@Url.Action("Index", null, new { area = string.Empty, controller = "User" }, Request.Url.Scheme)">
<span>Clients</span>
</a>
The result would have http://localhost/10000 (or with whatever port you are using) to be appended to the URL structure like:
http://localhost:10000/Users
I hope this helps.