Session Timeout ( passport pre-enrollment Page)

Sites like that and financial banking are time sensitive and you need to complete your business when opening such sites or be actively working on that site for it to verify your not a BotNet faking as a real person. You need to finish that sensitive site before surfing the internet. This isn't a Browser issue but sites like that are time sensitive and inactive request on that site will be logged out for "Security" purpose of identity thefts.