do you mean you want to hide the whole address bar? or just prevent the user from seeing the address of the page they are at?
if you want to hide the whole address bar you can launch your page in a new window using the code...
onLoad="window.open('[url for new page]','[name of new window','address=no');"
...but, if you just want to hide the address of a specific page, you could put the page into a frame, and the url of the frames page will appear in the address bar.
although, i'm not entirely sure why you'd want to do this.
ss