A Word About The alt Attribute...

First, it is required by HTML! And it has several purposes, the most significant of which is that the text for the alt attribute is what displays in the browser while the image is loading, or if the image doesn't load (for example, the user can set an option to prevent downloading of images).

Second, browsers display the text from the alt attribute when you hold your cursor over an image. The alt tag is a great way to provide some additional information or assistance for images. Hold the cursor over one of the navigation buttons on this page...see what happens?

Finally, the alt tag is used by machines that "read" web pages, such as machines for the blind. So, you can see it is particularly important to use text that reflects the nature of the graphic, particularly if it is an image that is used for navigation!