Here is a good article that explains this
Each page has an option to turn off the ViewState for. All you need to do it go to Sitefinity > Pages, select a page, select Properties tab, expand More Options and you will find the checkbox there which states "Disable ViewState". Also you cannot disable the entire view state.
Sitefinity itself does not work with session at all. If you are going to make some changes to the page object you have to inherit from the InternalPage class.
the Telerik team
Do you want to have your say in the Sitefinity development roadmap? Do you want to know when a feature you requested is added or when a bug fixed? Explore the Telerik Public Issue Tracking
system and vote to affect the priority of the items