in generel case after session invalating a session if u press back button it goes back to the previous page write this code this this code it will not happen in iexplorer
response.setHeader("Expires", "sat,6 May 1995 12:00:00 GMT");
response.setHeader("cache-control", "no-store,no-cache,must-revalidate");
response.addHeader("cache-control","post-check=0,pre-check=0");
response.addHeader("pragma", "no-cache");
