How to get visitor's MAC address in ASP.NET?

No, you can't. MAC address is not included in request IP header.

Using Cross Origin Resource Sharing (CORS) in ASP.NET Web API

http://www.codeguru.com/csharp/.net/net_asp/using-cross-origin-resource-sharing-cors-in-asp.net-web-api.html

How to solve problem “The type 'System.Web.Mvc.ModelClientValidationRule' exists in both” when try open MVC3 project after installed MVC4

Simplest way:
Open project references list, and remove System.Web.WebPages.from references

http://stackoverflow.com/questions/7510484/modelclientvalidationrule-conflict

How to login into ASP.NET webforms site by HttpWebRequest

http://odetocode.com/articles/162.aspx

private void Button5_Click(object sender, System.EventArgs e)
{
// first, request the login form to get the viewstate value
HttpWebRequest webRequest = WebRequest.Create(LOGIN_URL) as HttpWebRequest;
StreamReader responseReader = new StreamReader(
webRequest.GetResponse().GetResponseStream()
);
string responseData = responseReader.ReadToEnd();
responseReader.Close();

// extract the viewstate value and build out POST data
string viewState = ExtractViewState(responseData);
string postData =
String.Format(
"__VIEWSTATE={0}&UsernameTextBox={1}&PasswordTextBox={2}&LoginButton=Login",
viewState, USERNAME, PASSWORD
);

// have a cookie container ready to receive the forms auth cookie
CookieContainer cookies = new CookieContainer();

// now post to the login form
webRequest = WebRequest.Create(LOGIN_URL) as HttpWebRequest;
webRequest.Method = "POST";
webRequest.ContentType = "application/x-www-form-urlencoded";
webRequest.CookieContainer = cookies;

// write the form values into the request message
StreamWriter requestWriter = new StreamWriter(webRequest.GetRequestStream());
requestWriter.Write(postData);
requestWriter.Close();

// we don't need the contents of the response, just the cookie it issues
webRequest.GetResponse().Close();

// now we can send out cookie along with a request for the protected page
webRequest = WebRequest.Create(SECRET_PAGE_URL) as HttpWebRequest;
webRequest.CookieContainer = cookies;
responseReader = new StreamReader(webRequest.GetResponse().GetResponseStream());

// and read the response
responseData = responseReader.ReadToEnd();
responseReader.Close();

Response.Write(responseData);
}

How to add static html in ASP.NET MVC site?

Need to change routing setting in Global.asax.cs file like following:

        public static void RegisterRoutes(RouteCollection routes)
        {
            routes.IgnoreRoute("{resource}.html/{*pathInfo}");
        }