The back button will take you to the previous page. That is its function in all browsers.
But perhaps you mean the backspace key? I have had issues with this. Depending on current focus, it sometimes take you to the previous page. If you were filling out a form this can have the effect of erasing it. Two things can help.
1. Use keyboard only when navigating a form. This saves you having the focus outside a text field (happens with the mouse) when hitting backspace.
2. Don't use the backspace key. Use the Delete key instead.
3. Edit all the text in your favourite text editor, then copy & paste to where it belongs on the page.
Sorry, that is three things. Three things can help.
And a fanatical devotion to the pope.
Four things.