function menuOpen(a) {
obj = document.getElementById(a); 
if(obj){
obj.style.visibility="visible";
}
}

function menuClose(a) {
obj = document.getElementById(a); 
if(obj){
obj.style.visibility="hidden";
}
}


function checkform_contact(f)
  {
  if (document.getElementById('contactform').elements['contactpersoon'].value == "")
    {
    alert("Vul de naam van uw contactpersoon in.");
    window.setTimeout("window.document.contactform.elements['contactpersoon'].focus()",500);
    return (false);
    }
  if (document.getElementById('contactform').elements['adres'].value == "")
    {
    alert("Vul uw adres in.");
    window.setTimeout("window.document.contactform.elements['adres'].focus()",500);
    return (false);
    } 
  if (document.getElementById('contactform').elements['postcode'].value == "")
    {
    alert("Vul uw postcode in.");
    window.setTimeout("window.document.contactform.elements['postcode'].focus()",500);
    return (false);
    }  
  if (document.getElementById('contactform').elements['woonplaats'].value == "")
    {
    alert("Vul uw woonplaats in.");
    window.setTimeout("window.document.contactform.elements['woonplaats'].focus()",500);
    return (false);
    }   
  if (document.getElementById('contactform').elements['telefoon'].value == "")
    {
    alert("Vul uw telefoonnummer in.");
    window.setTimeout("window.document.contactform.elements['telefoon'].focus()",500);
    return (false);
    }    
 if (document.getElementById('contactform').elements['email_adres'].value == "")
    {
    alert("Geen e-mail ingevoerd.");
    window.setTimeout("window.document.contactform.elements['email_adres'].focus()",500);
    return (false);
    }
  else document.getElementById('contactform').submit();		
  }

function checkform_offerte(f)
  {
if (document.getElementById('offerteform').elements['contactpersoon'].value == "")
 {
alert("Vul uw contactpersoon in.");
window.setTimeout("window.document.offerteform.elements['contactpersoon'].focus()",500);
return (false);
}
if (document.getElementById('offerteform').elements['adres'].value == "")
 {
alert("Vul uw adres in.");
window.setTimeout("window.document.offerteform.elements['adres'].focus()",500);
return (false);
}
if (document.getElementById('offerteform').elements['postcode'].value == "")
 {
alert("Vul uw postcode in.");
window.setTimeout("window.document.offerteform.elements['postcode'].focus()",500);
return (false);
}
if (document.getElementById('offerteform').elements['woonplaats'].value == "")
 {
alert("Vul uw woonplaats in.");
window.setTimeout("window.document.offerteform.elements['woonplaats'].focus()",500);
return (false);
}
if (document.getElementById('offerteform').elements['telefoon'].value == "")
 {
alert("Vul uw telefoon in.");
window.setTimeout("window.document.offerteform.elements['telefoon'].focus()",500);
return (false);
}
if (document.getElementById('offerteform').elements['email'].value == "")
 {
alert("Vul uw email in.");
window.setTimeout("window.document.offerteform.elements['email'].focus()",500);
return (false);
}
else document.getElementById('offerteform').submit();
}