ALT Attribute: Use the alt attribute to provide descriptive text for the Image. For example: If there is an image in your website when clicked it will send a mail to a particular visitor email address, in this case your alt attribute values should be “by clicking on this image, an email will be sent your email address”. Don’t stuff your keywords in the alt attributes, most of the search engines consider as a Spammy method, it may result in a penalty for your sites ranking
Guidelines on Alt Attribute:
a. Always add alt attributes to images, Alt is mandatory for accessibility and for valid XHTML.
b. For images that play only a decorative role in the page, use an empty alt (i.e. alt="")
c. CSS background image so that reading browsers do not bother users by uttering things like "spacer image".
d. Choose a logical file name that reinforces the keywords.
e. Label the file extension. For example, if the image search engine sees a ".jpg" (JPEG) file extension
f. Make sure that the text nearby the image that is relevant to that image.
g. Again, do not lose a great opportunity to help your site with your images in search engines.
