// Navigates to the URL in the address box when 
// the ENTER key is pressed while the ToolStripTextBox has focus.
private void toolStripTextBox1_KeyDown(object sender, KeyEventArgs e)
{
    if (e.KeyCode == Keys.Enter)
    {
        Navigate(toolStripTextBox1.Text);
    }
}

// Navigates to the URL in the address box when 
// the Go button is clicked.
private void goButton_Click(object sender, EventArgs e)
{
    Navigate(toolStripTextBox1.Text);
}

// Navigates to the given URL if it is valid.
private void Navigate(String address)
{
    if (String.IsNullOrEmpty(address)) return;
    if (address.Equals("about:blank")) return;
    if (!address.StartsWith("http://") &&
        !address.StartsWith("https://"))
    {
        address = "http://" + address;
    }
    try
    {
        webBrowser1.Navigate(new Uri(address));
    }
    catch (System.UriFormatException)
    {
        return;
    }
}

// Updates the URL in TextBoxAddress upon navigation.
private void webBrowser1_Navigated(object sender,
    WebBrowserNavigatedEventArgs e)
{
    toolStripTextBox1.Text = webBrowser1.Url.ToString();
}