Website works only after clearing safari browser cache

I am facing a bizarre problem. When i open my website in iphone safari browser and then minimize it and leave it for sometime and then again open safari and try to navigate to some other page in the site it shows error. The error comes because i try to access values from session. The first time the user opens my site i start the session and save the site specific color values in it. Each time the next page is requested i fetch the values from session and replace in the inline css. The issue seems to be with the session. Once i get the error i cannot use the site. Even after refreshing the page the first page works but the error on navigating to other pages still exists. To get rid of this i need to clear the cache and refresh the page. Clearing the cache is a temporary workaround and the end users don't expect this behavior. Help me please i got stuck in this issue for a month. I want to add that i have set session.gc_maxlifetime to 12 hours , session.cookie_lifetime to 0.