An alt attribute is used to specify alternative text. It is used to replace an image. That means that it serves the same function as the image. Users of screen-readers, language translation applications or some hand-held devices cannot directly access pictures and other graphics. Similarly, some users choose to turn picture loading off- especially those with slower dial-in connections. These users rely on alt attributes.
An HTML attribute which is short for 'alternative text'. Alternative text is any text that can be seen when the graphics are turned off or when the mouse is run over the graphics.
Also known as "alt tag" in HTML language, alt attribute is specified for an Image and within the image tag. Its syntax is: IMG SRC="logo.gif" ALT="your website Logo" The text "your website Logo" will be displayed where your image "logo.gif" is placed while it is being loaded or if for any reason the image can't be displayed.