Search engines love text. If you think about it logically, computers can read and even interpret text. However, it's much more difficult to interpret a photo or image. Pictures are truly "worth a thousand words" to people, and we encourage website maintainers to utilize images effectively. We have a few rules-of-thumb to help maximize the effectiveness of your images in your search engine optimization strategy.
Images + Text
Images all have the opportunity to have associated text that Google and Bing can interpret to help determine what your page is all about. For instance, don't just put a picture of your company president up on the page. Attach their name to it through the use of "alt tags" and captions.
<div class="captioned-image"> <img src="tim_cook.jpg" alt="Photo of Tim Cook" /> <div class="caption">Apple CEO Tim Cook</div> </div>
In this technical looking example, a bit of HTML knowledge is useful, but not totally necessary to understand the concept. This code will produce an image with a caption underneath it. It also has the "alt text" Photo of Tim Cook attached to the photo itself.
Text attached to images in this way also has the side benefit of usability for visually impaired people - and even usability for all users.
Don't Use Unnecessary Images
With modern technologies like CSS3, it is increasingly unnecessary for great looking websites to use images instead of text. In the past, page titles and navigation elements would have been built out of images. Now we can create navigation our of simple lists and some nicely designed styling. Page titles can now utilize lots of different fonts and can be styled with amazing flexibility. Never use an image when text will do.
Your Image Names Matter
This might not seem obvious, but it makes sense when you think about it. In the example above, the photo file was named tim_cook.jpg instead of something like cam_img_097.jpg.
Image Size Matters
Modern smartphones like the iPhone 5 can produce 8 megapixel images. For most websites, 1 megapixel - or even smaller - is what is needed. If you don't optimize your image file size, you may be slowing your website down by as much as a factor of 10! Our website clients have tools built-in to their websites to automatically optimize their images to whatever sizes are needed on the website. This is especially helpful when a "thumbnail" version is needed as well as a more full-size version. Tools like Photoshop and pixlr.com can also help in resizing your images.