Hi dear friends, I have a custom asp.net control.

public class Window : WebControl {
    protected override void RenderContents(HtmlTextWriter wr) {
        wr.AddAttribute("runat", "server",true);
        wr.AddAttribute("id", this.UniqueID, false);
        wr.RenderBeginTag(HtmlTextWriterTag.Div);
        wr.RenderEndTag();
        wr.WriteLine();
        base.RenderContents(wr);
    }
}

And this is my result after compile and use the control:

<cc1:Window ID="Window1" runat="server" />

Use standard definition DIV with standard format:

<div runat="server" id="aaaa"></div>

After compile my web page to use this web custom control, this is render browser source of my web page:

<span id="Window1"><div runat="server" id="Window1"></div></span>
<div id="aaaa"></div>