You can right click on a tab, and check "Lock this tab". If this is enabled, the tab will show a confirmation popup if you try to close it. This can be useful if you often find yourself accidentally clicking links off a page, and losing whatever was previously on the page once you go back (because the content of the page changes after every reload).
The confirmation mechanism seems to only work for a tab that you have clicked inside of at least once. There doesn't seem to be a way for me to fix this.
