Get the URl From Firefox and Opera :
DdeClient dde = new DdeClient(browser, "WWW_GetWindowInfo");
dde.Connect();
string url = dde.Request("URL", int.MaxValue);
string[] text = url.Split(new string[] { "\",\"" }, StringSplitOptions.RemoveEmptyEntries);
dde.Disconnect();
return text[0].Substring(1);
Download NDde dll and add reference, and use as name space
SHDocVw.InternetExplorer browser;
string myLocalLink;
mshtml.IHTMLDocument2 myDoc;
SHDocVw.ShellWindows shellWindows = new SHDocVw.ShellWindows();
string filename;
foreach (SHDocVw.InternetExplorer ie in shellWindows)
{
filename = System.IO.Path.GetFileNameWithoutExtension(ie.FullName).ToLower();
if ((filename == "iexplore"))
{
browser = ie;
myDoc = browser.Document;
myLocalLink = myDoc.url;
MessageBox.Show(myLocalLink);
}