How to Resolved Answer Posted
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<asp:RadioButton ID="Rad1" runat ="server" />
<asp:Button ID="Bt_Submits" runat ="server" Text ="Answer" onclick="Bt_Submits_Click" />
<div id="div1" runat ="server">
Message helpful for all.
</div>
protected void Bt_Submits_Click(object sender, EventArgs e)
{
div1.Attributes.Add("style", "background-color :Silver;");
}