column.tooltip : stringDefault: undefined

    
 <table id="grid"></table>
 <script>
     $('#grid').grid({
         dataSource: '/0_6/Grid/GetPlayers',
         columns: [
             { field: 'ID', tooltip: 'This is my tooltip 1.' },
             { field: 'Name', tooltip: 'This is my tooltip 2.' },
             { field: 'PlaceOfBirth', tooltip: 'This is my tooltip 3.' }
         ]
     });
 </script>