Meta http-requiv="refresh" autoload with 2nd refresh killed my session variable

I have incorporated the tag <meta http-equiv="refresh" content="20"> into my ssp file in order to refresh the page every 20 seconds. The first auto refresh works fine. However, after the second 20-sec refresh, my session variable got killed.

Please kindly advise if this is normal. How can I fix the issue such that the page will refresh every 20 seconds without killing my session variable?