Alt Image Attribute Usage – Hear It From Google
Dont’ forget your alt tags! Not only does it provide valid XHTML coding standards but, it adds another layer of keywords that can be added to your page to help improve your SEO efforts. Images used in websites that have keywords in the alt tags provide Google with information regarding what the image is if, they are used right.
Matt Cutts, the head of Google’s web spam team describes which ones are important in this video: