While working on one of my own projects tonight, I found an issue with backspacing in Firefox. Sometimes when I would try to use backspace, I was not selected on the textarea. This causes firefox to go back one page in the browsers history. This is not the required action after adding multiple lines of code. So after a quick google I found an fix for this.

• First open your about:config (by typing it in your address bar).
• You will be brought to a configuration page that has a filter bar.
• Type browser.backspace in the filter.
• Finally modify the value from 0 to be 2. This will cause backspace to do nothing.

For more details see this website:
http://www.macosxtips.co.uk/index_files/change-backspace-behaviour-firefox.html