Getting logged off in another tab in mobile version

Hi, why do I have to login again whenever a new tab opens up in the mobile version but not login again when I'm on my computer version? It's kind of getting annoying where we have to login again to go to a certain I-F link like if I want to open up a FF thread or another topic, either a new tab pops up or if I copy the link it still shows that I have to login again...why should I login again in a different tab that pops up when I'm already online on I-F???