Accessibility is simply good practice in web development, but it also helps with site optimizing for search engine ranking. Adding an alt tag to your images can have a larger impact than simply having a text representation of the image for users who are not seeing your images–it can help to drive traffic to your site.
If you have ever used Google Image Search you know that when you find the image you are looking for and click on it, you are directed to the site that is hosting that image. Chances are good that if your site is about cooking and you have a well-optimized image of an apple pie in your article about apple pies, that user who just arrived at your site from her google image search, may have found a new source for recipes on the web in your site.
Some may argue that the conversion rate on image search (converting browsers to loyal readers) is pretty low, but the reality is that images are becoming increasingly more important in Site Optimizing. Unless you haven’t used Google in a couple of years, you will notice that search results now typically include images and other rich media.
So, let’s start with the Alt Tag which is simply an HTML tag that provides alternative text when an image or other non-textual element is not displayed. This happens, for instance, when a blind user accesses the page using audio-based technology. And since automated indexing programs (the robots that scour the web for search engines) are essentially blind to your page, the Alt Tag is the only thing they can recognize and utilize as part of the page’s content.
Be descriptive but keep Keywords in mind
When you write your Alt Tag, be descriptive for the accessibility factor–a blind person cannot tell that “pie-1” is really a “scrumptious cherry pie with lattice top crust”, but also keep in mind the keywords for your article and try to include them in the Alt Tag.
You should also try to name your image using the same keywords: If your image is alternatively called “Baked French Toast” you could name the file “baked-french-toast.jpg”. The name of the image files you use should also be keyword-rich to improve the relevance of the image to the search engine. Another trick would be to file the images using keyword-rich directories. For example, if your article is about making baked french toast for breakfast, you might have the image stored here: www.mycookingsite.com/images/breakfast/baked-french-toast.jpg
That is the overview on optimizing images for your web pages. If you are using Joomla to render your pages, optimizing images requires a bit more work, but is well worth the effort. This article covers optimizing in Joomla.