javascript error object required

<script type="text/javascript">
    function change(lnk,evt)
    {
        if(evt.type == "mouseover")
        {
            lnk.style.color = "red";
            lnk.style.fontSize = "60";
            document.getElementById('<%= tbl123.ClientID %>').style .visibility ="visible";
            document.getElementById('tbl123').style .display="block";
        }
        else if(evt.type == "mouseout")
        {
            lnk.style.color = "blue";
            lnk.style.fontSize = "20";
            document.getElementById('<%= tbl123.ClientID %>').style .visibility ="hidden";
        }
    }
    </script>

<asp:TableRow Width="100%" SkinID="SkinRow" runat="server">
           <asp:TableCell Width="100%" >
               <asp:LinkButton ID="lnk" runat="server" Text="mangal" onmouseover="change(this,event);"
                   onmouseout="change(this,event);"></asp:LinkButton>
               <asp:Table ID="tbl123" runat="server" Visible="false">
                   <asp:TableRow runat="server">
                       <asp:TableCell runat="server"></asp:TableCell>
                   </asp:TableRow>
                   <asp:TableRow>
                       <asp:TableCell runat="server" Text="mangal123">mangal123</asp:TableCell>
                   </asp:TableRow>
                   <asp:TableRow>
                       <asp:TableCell runat="server" Text="mangal1234556">mangal1234556</asp:TableCell>
                   </asp:TableRow>
               </asp:Table>
           </asp:TableCell>
       </asp:TableRow>