Formulario + campos obligatorios + menus desplegables

[Elisa85]

Código:

function validar(form)
{
if(form.nomCognoms.value==""){
alert("Completi el nom i cognoms");
form.nomCognoms.focus();
return false;
}

}
</script>
<form action="nouusuari.php" method="post">
...formulario
<input name="enviar" type="submit" value="Entrar" onClick="return validar(this.form)" > 
</form>