Providing security to website

For back button security you can use the following code in page behind:

protected override void OnPreRender(EventArgs e)
    {

        base.OnPreRender(e);

        string sb;

        sb = "";

        Page.RegisterClientScriptBlock("clientScript", sb);

    }

To disable browser chaching use
Response.Cache.SetCacheability(HttpCacheability.NoCache);
on page_load()

Use to disable back button