Recently, I was browsing a mobile friendly website but all of a sudden Nokia Browser just refused to work further. I would still have no problem using the phone (for example, holding down the menu button will still pull up the switch applications bar) but when I am in the Nokia Browser, nothing will react, hence, I can't even exit the program.
I had to force quit on the Nokia browser. To do so, press and hold the menu button until the application switch bar appears, select the application you want to force quit, then press "c" or delete button. It will ask if you want to exit that program. Choose "yes" and you are done.