Use the Alternative Text Attribute
Be sure to include the alt text attribute in your image tag.
The ALT attribute of the image tag provides the browser with text information to be displayed whenever it is not possible to display the graphic.
This will show up if your image is broken, if your reader has turned off images in his or her browser, of if the reader is using a text-only browser. In addition, this is a simple way to ensure that visually impaired readers using a "text reader" device will have some sense of what the graphic is about.
Using the alt attribute adds valueand it doesn't increase the load time for the page.
Alt text is part of the image tag:
<img src="images/palette.gif" alt="mac system palette">
Always use the alt attribute. Alt text is most helpful to the viewer when it is descriptive of the graphic, but it can be anything you wish the viewer to see if the graphic cannot be displayed.