These are the tags that tell what a .gif or .jpg is. Adding ALT (Alternative) descriptions to your IMG tags is quick and easy. You don't have to do any complex HTML coding. An example of a ALT tag looks like this:

<img src="images/services-pic.jpg" width="100" height="78"
ALT="XYZ company's website optimization services">

If you use images in your Web pages, its good practice to include Alt text for every image that a visitor to your site will see. ALT tags filled with keywords can also be used to boost your keyword frequency and help you achieve better rankings