alt tag

An HTML tag that provides alternative text when Web pages are displayed without images. This text is helpful for the visually impaired or those who choose not to download images on Web pages in order to increase their surfing speed. With some browsers, this text appears when you put your mouse over an image and leave it there. It is not necessary for Web designers to put any text there, but if they include terms specific to the Web site, some of the search engines may list the site higher in their results.