The alt attribute provides an alternate text for an image, if the user for some reason cannot view it (because of slow connection, an error in the src attribute, or if the user uses a screen reader).
If a browser cannot find an image, it will display the value of the alt attribute:
Example
<img src="wrongname.gif" alt="HTML5 Icon" style="width:128px;height:128px;">
The alt attribute is required. A web page will not validate correctly without it.
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