By default the image from websites are resized according to how the Firefox's interface window is (minimized, maximized or else...)
This feature can be disabled, via the below prodecure:
- Open Firefox.
- In the address bar type the following command:
- Click on the "I'll be careful, I promise..." button
- In the Filter field type:
- Double click and modify the value from true to false.
- Close the about:config window and restart Firefox.