If you mean download the source of a webpage...
using System;
using System.IO;
using System.Net;
And the function...
public static void SaveSource(string url, string path)
{
WebClient client = new WebClient();
string source = client.DownloadString(url);
File.WriteAllText(path, source);
}
For faster results of getting the source of a webpage, you may want to look into HttpWebRequests.