use of alt attribute in img tag code example
Example: html img alt
<!-- The required alt attribute specifies an alternate text for an image,
if the image cannot be displayed (screen reader...). -->
<img src="img_girl.jpg" alt="Girl in a jacket" width="500" height="600">
<img src="img_girl.jpg" alt="Girl in a jacket"
longdesc="img_girl-longdesc.html"> <!-- long description -->