A Firefox add-on that allows accidentally opened tabs to be dismissed with a single button press.
Here is more about this incredible Firefox extension:
Excess tabs on the awesome bar can be annoying. Ever open a new tab to perform a search, and then realize you didn’t need it? With OopsTab, you can quickly dismiss this new, unused tab with the press of the ESC button. OopsTab allows you to open and close tabs without ever having to touch the mouse, saving seconds in your web browsing life.
Want to learn more? Check it out at the Firefox Add-ons website.