Using CSS & HTML Select Row command sample code
<asp:GridView ID="GridView1"
runat="server"
CellPadding="2"
AutoGenerateColumns="False" Width="500px">
<Columns>
<asp:BoundField DataField="ProductID" HeaderText="ProductID">
<HeaderStyle HorizontalAlign="Left" />
</asp:BoundField>
<asp:BoundField DataField="ProductName" HeaderText="Product Name">
<HeaderStyle HorizontalAlign="Left" Width="200px" />
</asp:BoundField>
<asp:BoundField DataField="UnitsInStock" HeaderText="Units In Stock">
<HeaderStyle HorizontalAlign="Left" />
<ItemStyle HorizontalAlign="Center" />
</asp:BoundField>
<asp:BoundField DataField="UnitPrice" HeaderText="Price Per Unit">
<HeaderStyle HorizontalAlign="Left" />
<ItemStyle HorizontalAlign="Center" />
</asp:BoundField>
<asp:CommandField HeaderText="Select" ShowHeader="True"
ShowSelectButton="True">
<HeaderStyle HorizontalAlign="Left" />
</asp:CommandField>
</Columns>
<SelectedRowStyle BackColor="#FFFFBB" Font-Bold="True" />
</asp:GridView>
Another sample code here &
also here