On my quest to have Emacs bindings on my browser, and after noticing that is there a good extension available to Firefox, I chose switch from Chrome.
Unfortunately, upon opening the Firefox, very big texts, icons, toolbar were shown.
After some googling, I found out that just typing about:config in url bar, accessing the inner config of the browser, then set layout.css.devPixelsPerPx from -1 to 1.3 does the trick.
Nice! Now back to installing Firemacs extension…