This is pertinent to a phone.

I see many websites that use some kind of scripting to essentially disable the back button of your phone.
This is bad design because hardware and phone behavior should not be messed with.

There is a simple workaround for this.

Simply, refresh the page and hit the back button (while the page is loading).

Why does this work?
This is because you are hitting back before the javascript is loaded and takes over.