firing a button in aspx

[na]

Hello .

I have a buttons in a master page (<asp:button on an aspx page) that
when it fired an aspx page is displayed throught the cod bihend.

How come the path of the aspx file change when the button is fired for
the second time.

Here is my cod:

<asp:Button ID="Client" runat="server" Text="Espace client"
OnClick="Client_Click1" />

Cod bihend :
protected void Client_Click1(object sender, EventArgs e)
{
afiche_image();
//Session["catalogue"] = Client.ClientID.ToString();
Session["catalogue"] = Client.ClientID.ToString();
page = "";
page = "Page/catalogue/catalogue.aspx";
Response.Redirect(page);
}

It will be nice if anyone could help.

Waitting for your help