Hello,  

Please find the JavaScript code below. You can use the property cssText of cells  to set some style or manipulate it.

<ClientSideEvents CellClickHandler="CellManipulation" />

    <script type="text/javascript">

    function CellManipulation (gridId, cellId){

        var rowLength = igtbl_getGridById(gridId).Rows.length;

        var collId = igtbl_getCellById(cellId).Index;

        var collIdy = igtbl_getCellById(cellId);       

        for(var i = 0; i<rowLength; i++){

            igtbl_getCellById('UltraWebGrid1_rc_' + i + '_' + collId).Element.style.cssText="font-size-adjust: 0.3; text-align: center;";

        }

      }

    </script>

I hope this helps.