C#

<code>
[WebMethod(Description="Login Operation")]
public string Login(string userName,string password)
{
HttpWebRequest req = (HttpWebRequest) HttpWebRequest.Create("http://[www.desiredsite.com/login.aspx?name="+userName+"&password="+passWord)
req.KeepAlive = false;
HttpWebResponse resp = (HttpWebResponse) req.GetResponse();			
StreamReader sr = new StreamReader(resp.GetResponseStream(), System.Text.Encoding.UTF8);	
string all = sr.ReadToEnd();//So far you send the info, thus you get string having the result page 
...//In these lines of code , regarding to the html structure, you should wrap the info you need
...// clean up the unnecessary tags and find whether the login is succeeded or not by manipulating html
...
return resultString;//This will be the web service's respond string to the application.
</code>