you may disable back button : using JavaScript
<script type="text/javascript" language="javascript">
function DisableBackButton() {
window.history.forward()
}
DisableBackButton();
window.onload = DisableBackButton;
window.onpageshow = function(evt) { if (evt.persisted) DisableBackButton() }
window.onunload = function() { void (0) }
</script>
We can also achieve this by disabling browser caching in code behind write the following lines of code in Page_Init event or Page_Load event and don’t forgot to add namespace using System.Web; because HttpCacheability related to that namespace.
protected void Page_Init(object sender, EventArgs e)
{
Response.Cache.SetCacheability(HttpCacheability.NoCache);
Response.Cache.SetExpires(DateTime.Now.AddSeconds(-1));
Response.Cache.SetNoStore();
}