Text alternative for banner ad images

The HTML alt attribute for <img> tag is served as a text alternative to image. It is used to add text-only information for an ad image when that image cannot be displayed. This setting also serves as the window's title when this ad is displayed as a pop-up or pop-under ad, or the title of interstitial ad page. Below is an example in HTML:

<img src="AdImage.gif" alt="Some alternative ad copy" />