Here’s a little exercise: on the top menu of your web browser, find the “View Source” command, usually under the View of Display menu depending on what browser you’re using.
This will open up the source code of the web page you are looking at and is the way that search engine spiders (the automated programs that index your website) see your web pages. Notice that there are no images displayed in the source, only text and image filenames. That means the all of the images on your website are, to the search engine’s eyes, nothing but collections of text.
No matter how wonderful and content-rich your images may be, they will do nothing to help your search engine ranking, unless you do something about it.
The first thing to alter is the alt text of your images. Put your mouse cursor over an image and hold it in place. Does a little text box pop up with a description of the image? If so, then you are seeing the alt text, if there is nothing, then there has been no alt text entered for that image.
There are both benefits and drawbacks to alt text, so not everybody uses it for every image. If you’ve already got adequate keyword and phrase saturation in your web content, then image alt text may be a bit overkill for your site and that may hamper your rankings, due to search engines’ aversion of keyword oversaturation.
If, however, your website is dependent on images, for instance if you are promoting art work or some other strictly visual medium, then alt text will allow you to add in the keywords and phrases that will help your site get ranked.
Is alt text for you? That depends on your own site, but you should at the least be aware of it as an SEO option.