function setColor(el, bg) {
  if (el.style) el.style.backgroundColor = bg;
}

function checkInput(form) {
  var bgBad = "#FF0000";
  var bgGood = "white";
  var valid = true;
  if (form.name.value == "") {
    valid = false;
    setColor(form.name, bgBad);
  } else {
    setColor(form.name, bgGood);
  }
  if (form.date.value == "") {
    valid = false;
    setColor(form.date, bgBad);
  } else {
    setColor(form.date, bgGood);
  }
  if (form.adress.value == "") {
    valid = false;
    setColor(form.adress, bgBad);
  } else {
    setColor(form.adress, bgGood);
  }    
  if (form.email.value == "") {
    valid = false;
    setColor(form.email, bgBad);
  } else {
    setColor(form.email, bgGood);
  }
  if (!valid) alert("Tjek at du har udfyldt de felter der er markeret med ( * ) og at din email adresse er korrekt");
  return valid;
}