The name explained it
当前为
This script will force Firefox to show broken image icon when image failed loading, wether the image has alt attribute. You can press Alt+R to reload the broken images.
這個Script會強制Firefox顯示圖片載入失敗的圖示，即使圖片有alt屬性。 按Alt+R會重新載入失敗的圖片。
Image without alt. you should see the icon by default.
<img src="https://i.am.broken">
Image with blank alt. By the default, you will see nothing.
<img alt="" src="https://i.am.broken">
Image with alt attribute. You should see the text in alt attribute.
<img alt="There used to be a image, but now it is broken" src="https://i.am.broken">
After installing the script:
!image.src.