wondering if I can do Html.RenderPartial("my user control path");

I added following code in _ColumnsThree.cshtml:

@{ this.Html.RenderPartial("~/Views/Shared/WebUserControl1.ascx"); }

and in my user control I have only sample text "Test" right now.

I am getting this error:
The partial view '~/Views/Shared/WebUserControl1.ascx' was not found or no view engine supports the searched locations. The following locations were searched:
~/Views/Shared/WebUserControl1.ascx

My eventual goal is to show News scroller using web user control (.ascx file)

I will appreciate if anyone can reply to this.

You're going to need to load up the control and render its contents.  Then instead of calling Html.RenderPartial, you'd call Html.Raw(resulting_html)...

Here's an example...  

*note, not tested...

@{
        string renderedControl = string.Empty;

        using(Page controlLoader = new Page())
        {

                WebUserControl1 viewControl = controlLoader.LoadControl("~/Views/Shared/WebUserControl1.ascx") as WebUserControl1; // I'm casting because the below example sets custom properties on the control.

                if(viewControl != null)
                {

                        // Populate any properties...
                        viewControl.Property1 = somevalue1;
                        viewControl.Property2 = somevalue2;

                        controlLoader.Controls.Add(viewControl);

                        StringWriter writer = new StringWriter();

                        Server.Execute(controlLoader, writer, false);

                        renderedControl = writer.ToString();
                }
        }
}

<div>@Html.Raw(renderedControl)</div>

Again, it's not tested, but something like this should work is you're dead-set on using an ASCX control.

-D