Highlight GridView row on mouseover by overriding CSS used in Itemstyle-CssClass

I am having the grid with 4 columns.Two Css class are applied alternatively for each columns in a row by using Itemstyle-CssClass Property of boundfield. Now my requirement is Onmouseover on the row,that row should get highlighted with some color,and onmouseout,the old cssclass of each column in that row should be reset.The first problem is I can't override the CSS specified in Itemstyle-CssClass from client side. If the First problem get solved,then how to backup the old CSS applied in each column of that row and reapply it on mouseout. My code aspx page --------------- <%@ Page Language="vb" AutoEventWireup="false" CodeBehind="Default.aspx.vb" Inherits="Grid_Highlight._Default" %> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" > <head id="Head1" run ...