Ok after some research i found that this is a common problem.
So... this is my solution...
i have an include page in all webpages on my website pages so i included the following within it..
My Session.timeout = 30
Within the include asp file i have ...
<% if Session("login") = "true" then %>
setTimeout( "_SessionExpired()", 31 * 60 * 1000 );
alert('Your Session had Expired')
location.href = "http://www.mydomain.com/";