Why don't you search in Google or Bing prior to post the question here?
If you have searched google, anything you have tried implementing?
Why exactly you want to hide the address bar?
You can do this programatically, by opening a new window (at least for IE).
Please check following links-
http://www.coderanch.com/t/118289/HTML-CSS-JavaScript/hide-address-bar[
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javascript - Hiding address bar in all browsers - Stack Overflow[
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If you need to mask the domain itself, even you can do that too.
Check
Domain masking - Wikipedia, the free encyclopedia[
^] for more details. This has to be done with the hosting panel.
NOTE: Unless it's really necessary, please do not take this approach for many reasons.
Hope, these help :)