Image alt tags are used by search crawlers to understand the content within a photo. If a photo fails to use the alt tag, search crawlers will not add the photo to its index. Often times, I find image alt tags being used sometimes, mis-used, or many of times not at all. Just recently I found one photo on a website that had received a very prestigious award. The alt tag was completely missing. Not only could search engines not read the value of the award but the equity of the award as tied to the law firm was not gaining search value equity.