Earlier this month, Bill Slawski wrote about how search engines use images to rank web pages. He explains that search engines often look at text, alt tags, and similar contextual elements to rank images. He also refers to a Microsoft patent that uses image scores to aid in rankings. This system considers the contents of an image (whether it has a person, is a photograph or not, etc.) with its position on a page and then its site level features (which may distinguish between navigational images versus one-time-only images).
On Cre8asite Forums, iamlost wonders if there are other elements that will impact the rankings. For example, do page layouts impact these rankings? Do CSS or HTML resizing of image dimensions impact the scores?
I suppose these could have open-ended questions at this time. However, yannis has responded with some good image optimization techniques.
- He says that you should enclose your images in divs (defined by a photo class).
- Image titles should be in h3s or larger.
- Images that you want search engines to know about should be 35-40% of the page size and should be on the top of the page.
- The image name is still important.
- Captions should be added to images.
- Never forget those ALT tags (but TITLE tags are not as important).
- You don't need LONGDESC.
- You can refer to the image from somewhere in your content to boost its relevance.
- EXIF information from images may be important in the future but it is not being used now.
- Search engines are getting smarter at figuring out what is in images (face recognition, for example).
- Use aesthetically pleasing images.
There's a pretty valuable ongoing discussion over at Cre8asite Forums with more member follow-up, so check it out.