function check_form(action){
	if(action == "cmb"){
		if(document.getElementById("cmb_naam").value == "Uw naam ..."){
			alert("U dient uw naam in te vullen.");
			return false;
		}
		else if(document.getElementById("cmb_tel").value == "Uw telefoonnummer ..."){
			alert("U dient uw telefoonnummer in te vullen.");
			return false;
		}
		else{
			return true;	
		}
	}	
}