'add the "Microsoft Internet Controls" reference in your VBA Project indirectly
Set ie = CreateObject("InternetExplorer.Application")
With ie
    .Visible = True
    .navigate ("https://online.nationalgridus.com/login/LoginActivate?applicurl=aHR0cHM6Ly9vbmxpbmUubmF0aW9uYWxncmlkdXMuY29tL2VzZXJ2aWNlX2VudQ==&auth_method=0")
    While ie.ReadyState <> 4
        DoEvents
    Wend
    Set username = .document.getElementById("uid") 'id of the username control (HTML Control)
    Set pwd = .document.getElementById("response") 'id of the password control (HTML Control)
    Set button = .document.getElementById("Submit") 'id of the button control (HTML Control)
    username.Value = "MasterAccountName1234"
    pwd.Value = "MasterAccountPassword1234"
    button.Click
    While ie.ReadyState <> 4
        DoEvents
    Wend
End With
Set ie = Nothing
End Sub