function validateForm ( form ) {
   for ( var e = 0; e < form.elements.length; e ++ ) {
      var el = form.elements [ e ];
      if ( el.type == 'text' || el.type == 'textarea' ||
         el.type == 'password' || el.type == 'file' ) {
         // check text fields
         if ( el.value == '' ) {
            alert ( 'Please fill out the ' + el.name + ' field' );
            el.focus ( );
            return false;
         }
      }
      else if ( el.type.indexOf ( 'select' ) != -1 ) {
         // check selectable dropdown menus
         if ( el.selectedIndex == -1 ) {
            alert ( 'Please select a value for ' + el.name );
            el.focus ( );
            return false;
         }
      }
      else if ( el.type == 'radio' ) {
         // check radio button groups
         var group = form [ el.name ];
         var checked = false;
         if ( !group.length ) checked = el.checked;
         else
            for ( var r = 0; r < group.length; r ++ )
               if ( ( checked = group [ r ].checked ) )
            break;
         if ( !checked ) {
            alert ( 'Nincs minden kérdés kitöltve!' );
            el.focus ( );
            return false;
         }
      }
      else if ( el.type == 'checkbox' ) {
         // check checkbox groups
         var group = form [ el.name ];
         if ( group.length ) {
            var checked = false;
            for ( var r = 0; r < group.length; r ++ )
               if ( ( checked = group [ r ].checked ) )
            break;
            if ( !checked ) {
               alert ( 'Nincs minden kérdés kitöltve!' );
               el.focus ( );
               return false;
            }
         }
      }
   }
   return true;
}