how to avoid lose session?thank u very much

hi

   i 'd like to ask for help.

  sometimes,when the page is reloaded,or sessions are transfered between webpages,the sessions are lost(they become null)

  my web config is like that:

   <sessionState cookieless="true"
      regenerateExpiredSessionId="true"
                  timeout="50"></sessionState>

  is there any friends could do me a favor to give me suggestions?

 thank u very much in advance your kindness help

best regards

martin