What does it mean alt=""
Suppose you have attached an image with code like <img src="file1.png"> and unfortunately file could not load then the 'alt' will work , it shows the alternative information about the image if you do so like <img src=file1.png"alt="Nature Image">, and alt="" means no information to be use as alternative in case of unprocessed contents...
alternate.if the path of the image is not clear or if any other error occur,what you write in the alt attribute will be displayes
alt is alternative information. alt="" means no alternative information
alt provide an additional information to the given content.... but alt ="" means no additional information