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What you want to do is not possible - and if it was, it would be considered by an overwhelming majority of site visitors as "hijacking" their screen: hiding browser chrome (like the back button) would make people feel that they had been trapped, and you'd very likely lose every visitor you got, never to return.
It is possible to open a popup window full screen, however anyone with a popup-blocker wouldn't get to see it, and it is almost as bad as the above scenario.
I would strongly suggest finding another, more user-friendly strategy. Basically, you need to adapt to the user's needs, not adapt their browser window to your design.
You'll find that this is not something that is part of the web as a medium. It is often a concept that comes from a background in design or in creating applications, where this kind of thing IS part of the medium.
But trying to do it on a web site is something like using oil paint on watercolor paper, and it will work against your ultimate purposes on the web.
