2.2.15 [W3C-HTML52] Section 4.7.5. The img element

C0021: No image indicator is shown when the image is unavailable

The specification states:

 ... The img element
     ...
     What an img element represents depends on the src attribute and the alt attribute.
  
         If the src attribute is set and the alt attribute is set to the empty string
             ...
             ... User agents may provide the user with a notification that an image is 
             present but has been omitted from the rendering.

EdgeHTML Mode

No image indicator is shown when the image is unavailable. If alt text is available that text will be shown.

C0019: Images are obtained immediately

The specification states:

 ... The img element
     ...
     In a browsing context where scripting is disabled, user agents may obtain images 
     immediately or on demand. ...

EdgeHTML Mode

Images are obtained immediately.