function validacao_login(f) {
  if (f.login.value.length==0) {
    alert("Login Field Required"); 
    return false;
  }

  if (f.password.value.length==0) {
    alert("Password Field Required");
    return false;
  }
}

function validacao_registo(f) {
  if (f.email.value.length==0) {
    alert("E-mail Field Required");
    return false;
  }

  var controlar;
  controlar=/^\w+@\w{2,}(\.\w{2,})+$/.test(f.email.value);

  if (controlar==false) {
    alert("Invalid E-mail :: Ex: xxxxxx@abc.com");
    f.email.value="";
    return false;
  }

  if (f.login.value.length==0) {
    alert("Username Field Required");
    return false;
  }

  if (f.password.value.length==0) {
    alert("Password Field Required");
    return false;
  }

  if (f.cpassword.value.length==0) {
    alert("Password Field Required");
    return false;
  }

  if (f.password.value!=f.cpassword.value) {
    alert("Password fields don't match...");
    return false;
  }
}