asp.net 怎么安全退出问题

退出登录后,我先销毁session对象,然后跳转到登录界面,但是后退会还能回到刚才登录进出的页面,如果再刷新些页面就要重新登录了,这个问题怎么解决啊?
还有个问题,我用Response.Write(" <script language=javascript>alert(\"成功！\"); </script>")后,我刚才的居中排列的界面会变成靠左,这个过程由一个按纽的单击事件触发的.这又是为什么呢?

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用Response.Write会破坏格式!!
用
Page.ClientScript.RegisterStartupScript(Page.GetType(), "", "alert('成功！');", true);

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Response.Write会破坏页面样式
ClientScript.RegisterStartupScript(this.GetType(), "message", " <script language='javascript' defer>alert(''); </script>");
FormsAuthentication.SignOut();
Session.Clear();
Session.Abandon();
防止后退
<META content=no-cache>
<META http-equiv=Cache-Control content=no-cache>
<META http-equiv=Expires content=0>

Response.Cache.SetCacheability(System.Web.HttpCacheability.NoCache);
Response.Expires = 0;
Response.Buffer = true;
Response.ExpiresAbsolute = DateTime.Now.AddSeconds(-1);
Response.AddHeader("pragma", "no-cache");
Response.CacheControl = "no-cache";

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引用

Response.Write会破坏页面样式
ClientScript.RegisterStartupScript(this.GetType(), "message", &qu