Quick Peek for Firefox v0.0.3
Take a quick peek at links without leaving the current browser tab.
Use the contextmenu > Peek (Right-click or Cmd-click). You may use also use shortkey 'E'.
Click on the preview to open the link in a tab.
Press ESCAPE, Q or click anywhere outside the preview to close the preview.
A small animated GIF of how this works can be viewed here: https://github.com/j-angnoe/quick-peek-browser-extension.
This extension is open source for you to review.