Add a "Url" property to the model you are passing to the view and set it to _m.url, or put _m.url in the ViewBag and show that;
Controller;
ViewBag.Url = _m.url;
View
<li>Your ad is now live you can check through this link @ViewBag.Url</li>
Though you'll probably want to render an "a" tag to make it clickable.