How to Use the ALT Attribution for Images in WordPress
To extend SEO (search engine optimization) in WordPress, you can add keywords to your site by placing ALT attributes within in your image tags to further define and describe the images. You can accomplish this task by using the Alternate Text field in the WordPress image uploader. WordPress creates an environment that’s friendly to search engines, giving them easy navigation through your archives, categories, and pages.
When you use the WordPress image uploader to include an image in your post or page, you're given a Description text box in which you can enter a description of the image. This text automatically becomes the ALT attribute.
The ALT attribute’s real purpose is to provide a description of the image for people who, for some reason or another, can't actually see the image. In a text-based browser that doesn’t display images, for example, visitors see the description, or Alternate text, telling them what image would be there if they could see it. Also, the attribute helps people with impaired vision who rely on screen-reading technology because the screen reader reads the alternate text from the image.
You can read more about Web site accessibility for people with disabilities.
An extra benefit of the ALT attribute is that search engines gather data from them to further classify the content of your site. The following is the code for inserting an image with the ALT attribute:
<img src="http://yourdomain.com/image.jpg" alt="This is an ALT attribute within an image" />
Search engines harvest those ALT attributes as keywords. The WordPress image uploader gives you an easy way to include those ALT attributes without worrying about inserting them into the image code yourself. Just fill out the Description text box before you upload and add the image to your post.