function confirmEmail(emailField) {
          if (emailField.value != '') {
          
             var x = emailField.value;
             var filter = /^([a-zA-Z0-9_.-])+@(([a-zA-Z0-9-])+.)+([a-zA-Z0-9]{2,4})+$/;
             if (!filter.test(x)) {
                alert("The supplied email address appears to be invalid or incomplete. Please re-enter your email address.");
                emailField.value = '';
                emailField.focus();
             } 
          }
        }