How to display one control over another

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ASP.NET

I am generating asp.net project in which I want to put one control over another and make them visible true\false according to the list item selected from unordered list. I want to know how can I get which list item is selected from unordered list and how to place one control over other like what we can do easily in windows form. Code for unordered list is:

<ul id="nav" >
            <li class="srvlist"><a href="Default.aspx">Dashboard</a>
                <div class="sub1">
                <ul id="inner_nav">
                    <div class="arrow1"></div>
                    <li><a href="#">Recent</a></li>
                    <li><a href="#">All</a></li>
                </ul>
                </div>
            </li>
            <li class="srvlist"><a href="#">Statistics</a>
                <div class="sub1">
                <ul id="inner_nav">
                    <div class="arrow1"></div>
                    <li><a href="#">Opens</a></li>
                    <li><a href="#">Clicks</a></li>                        
                    <li><a href="#">Bounces</a></li>
                    <li><a href="#">Spams</a></li>                        
                    <li><a href="#">Unsubscribe</a></li>
                    <li><a href="#">Blocks</a></li>
                    <li><a href="#">Invalid Ids</a></li>
                </ul>
                </div>
            </li>
            <li><a href="#">Graph</a></li>                
            <li><a href="#">Compose</a></li>
        </ul>