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

function check(form)
  {
    var bgBad = "#0000cf";
    var bgGood = "white";
    var valid = true;
    var temp;

    if (document.contact.cusfirstname.value.length < 5)
      {
        valid = false;
        setColor(contact.cusfirstname, bgBad);
      }
    else
      {
        setColor(contact.cusfirstname, bgGood);
      }

    if (document.contact.cusaddress.value.length < 5)
      {
        valid = false;
        setColor(contact.cusaddress, bgBad);
      }
    else
      {
        setColor(contact.cusaddress, bgGood);
      }

    if (document.contact.cusnumber.value.length < 11)
      {
        valid = false;
        setColor(contact.cusnumber, bgBad);
      }
    else
      {
        setColor(contact.cusnumber, bgGood);
      }

    if (document.contact.custowncity.value.length < 5)
      {
        valid = false;
        setColor(contact.custowncity, bgBad);
      }
    else
      {
        setColor(contact.custowncity, bgGood);
      }

    if (document.contact.cuspostcode.value.length < 7)
      {
        valid = false;
        setColor(contact.cuspostcode, bgBad);
      }
    else
      {
        setColor(contact.cuspostcode, bgGood);
      }
    if (!valid) alert("Please fill out the entire form.");
    return valid;
  }