About Session timeout..

Question

Dear sir
I am a new developer. i developed a software in asp.net. i use login by session. but timeout is only 20 minute. but i wrote in web.config    <sessionState timeout="180"/> . It doesn't work.
i got a solution that <sessionstate mode="InProc" cookieless="true" timeout="180" />. it works. but problem is it changes my URL http://localhost:1369//ReportForm.aspx TO

http://localhost:1369/(S(iq01trbm1on1achaol45p3gq))/ReportForm.aspx 

and sometime report not show. 
how to solve it if anybody help me best regards.