function checkform ( form )
{

  // ** START **


if (form.name.value == "")
  {
    alert( "Please enter your Name." );
    form.name.focus();
    return false ;
  }


if (form.email.value == "")
  {
    alert( "Please enter your email address." );
    form.email.focus();
    return false ;
  }

// START confirm valid email address

if ((form.email.value.indexOf ('@',0) == -1 ||
   form.email.value.indexOf ('.',0) == -1) &&
   form.email.value != "")
  {
    alert( "The email address entered doesn’t seem to be valid." );
    form.email.focus();
    return false ;
  }

// END confirm valid email address



// START confirm entry in tel_no field is a number and not a letter

  var digits = "0123456789 ";

  for (var i = 0; i < form.tel_no.value.length; i++)
  {
    temp = form.tel_no.value.substring(i, i+1)

    if (digits.indexOf(temp) == -1 &&
     form.tel_no.value != "")
    {
    alert( "You must enter a number in telephone No." );
    form.tel_no.focus();
    return false ;
    }
  }

// END confirm entry in tel_no field is a number and not a letter






if (form.details.value == "")
  {
    alert( "Please enter your enquiry details." );
    form.details.focus();
    return false ;
  }


 if (form.contact.options[0].selected != ""){
    alert( "Please select how you wish to be contacted." );
    form.contact.focus();
    return false ;
  }


if (form.contact.value == "Phone")
  {
if (form.tel_no.value == "")
  {
    alert( "You have requested to be contacted by telephone but have not entered a telephone number." );
    form.tel_no.focus();
    return false ;
  }
  }


  // ** END **
  return true ;
}