function validate_required(field,alerttxt)
{
with (field)
{
if (value==null||value=="")
{alert(alerttxt);return false}
else {return true}
}
}

function validate_email(field,alerttxt)
{
with (field)
{
apos=value.indexOf("@")
dotpos=value.lastIndexOf(".")
if (apos<1||dotpos-apos<2) 
  {alert(alerttxt);return false}
else {return true}
}
}

function validate_form(thisform)
{
with (thisform)
{
if (validate_required(lastname,"Please enter your last last name")==false)
{lastname.focus();return false}
if (validate_required(phone,"Please enter your phone number")==false)
{phone.focus();return false}
if (validate_required(email,"Please enter your email address")==false)
{email.focus();return false}
if (validate_required(street,"Please enter your street")==false)
{street.focus();return false}
if (validate_required(city,"Please enter your city")==false)
{city.focus();return false}
if (validate_required(country,"Please enter your country")==false)
{country.focus();return false}
if (validate_required(persons,"Please enter the number of persons")==false)
{persons.focus();return false}
if (validate_required(arrival,"Please enter the date of arrival")==false)
{arrival.focus();return false}

myOption = -1;
for (i=thisform.accomodation_type.length-1; i > -1; i--) {
if (thisform.accomodation_type[i].checked) {
myOption = i; i = -1;
}
}
if (myOption == -1) {
alert("Please select an accomodation type");
return false;}

if (validate_email(email,"I think you've made a mistake with your email address")==false)
  {email.focus();return false}

}
}