function check_input(field_name, field_size, message) {
  if (form.elements[field_name] && (form.elements[field_name].type != "hidden")) {
    var field_value = form.elements[field_name].value;

    if (field_value == '' || field_value.length < field_size) {
      error_message = error_message + "* " + message + "\n";
      form.elements[field_name].className = "buttonfehler";
      error = true;
    }else{form.elements[field_name].className = "button";}
  }
}

function check_emailinput(field_name, field_size, message) {
  if (form.elements[field_name] && (form.elements[field_name].type != "hidden")) {
    var field_value = form.elements[field_name].value;

    if (field_value == '' || field_value.length < field_size || field_value.indexOf("@") <= 0 ) {
      error_message = error_message + "* " + message + "\n";
      form.elements[field_name].className = "buttonfehler";
      error = true;
    }else{form.elements[field_name].className = "button";}
  }
}

function check_select(field_name, field_default, message) {
  if (form.elements[field_name] && (form.elements[field_name].type != "hidden")) {
    var field_value = form.elements[field_name].value;

    if (field_value == field_default) {
      error_message = error_message + "* " + message + "\n";
      form.elements[field_name].className = "buttonfehler";
      error = true;
    }else{form.elements[field_name].className = "button";}
  }
}

function check_check(field_name, message) {
  if (form.elements[field_name] && (form.elements[field_name].type != "hidden")) {
    var field_value = form.elements[field_name].value;
    
    if (!form.elements[field_name].checked) {
      error_message = error_message + "* " + message + "\n";
      form.elements[field_name].className = "buttonfehler";
      error = true;
    }else{form.elements[field_name].className = "button";}
  }
}

function check_radio(field_name, message) {
  var isChecked = false;

  if (form.elements[field_name] && (form.elements[field_name].type != "hidden")) {
    var radio = form.elements[field_name];

    for (var i=0; i<radio.length; i++) {
      if (radio[i].checked == true) {
        isChecked = true;
        break;
      }
    }

    if (isChecked == false) {
      error_message = error_message + "* " + message + "\n";
      form.elements[field_name].className = "buttonfehler";
      error = true;
    }else{form.elements[field_name].className = "button";}
  }
}

function check_password(field_name_1, field_name_2, field_size, message_1, message_2) {
  if (form.elements[field_name_1] && (form.elements[field_name_1].type != "hidden")) {
    var password = form.elements[field_name_1].value;
    var confirmation = form.elements[field_name_2].value;

    if (password == '' || password.length < field_size) {
      error_message = error_message + "* " + message_1 + "\n";
      form.elements[field_name_1].className = "buttonfehler";
      error = true;
    } else if (password != confirmation) {
      error_message = error_message + "* " + message_2 + "\n";
      form.elements[field_name_2].className = "buttonfehler";
      error = true;
    }else{form.elements[field_name_1].className = "button";
    form.elements[field_name_2].className = "button";}
  }
}

function check_datum(field_name_d, field_name_m, field_name_y, field_default, message){
  if (form.elements[field_name_d] && (form.elements[field_name_d].type != "hidden") && form.elements[field_name_m] && (form.elements[field_name_m].type != "hidden") && form.elements[field_name_y] && (form.elements[field_name_y].type != "hidden")) {
    var field_d_value = form.elements[field_name_d].value;
    var field_m_value = form.elements[field_name_m].value;
    var field_y_value = form.elements[field_name_y].value;

 
    if ((field_d_value == field_default) || (field_m_value == field_default) || (field_y_value == field_default)){
     error_message = error_message + "* " + message + "\n";
     form.elements[field_name_d].className = "buttonfehler";
     form.elements[field_name_m].className = "buttonfehler";
     form.elements[field_name_y].className = "buttonfehler";
     error = true;     
    }
     else{
	 day_cor=parseInt(field_d_value,10);
	 month_cor=parseInt(field_m_value,10)-1;
	 
     var kontrolldatum=new Date(field_y_value,month_cor,day_cor);
     if (kontrolldatum.getDate()==day_cor && kontrolldatum.getMonth()==month_cor && kontrolldatum.getFullYear()==field_y_value){
     form.elements[field_name_d].className = "button";
     form.elements[field_name_m].className = "button";
     form.elements[field_name_y].className = "button";
     }
     else{
       
     error_message = error_message + "* " + message + "\n";
     form.elements[field_name_d].className = "buttonfehler";
     form.elements[field_name_m].className = "buttonfehler";
     form.elements[field_name_y].className = "buttonfehler";
     error = true;
     }     
     }
  }
}