@auntniniJan 13.2013 — #Cannot figure why SEO would differentiate between image file format. In any case, images should all have alt="alternate text" attribute, which is what would influence page "content" rating.
Have not gotten into SVG or APNG. Basic Web image formats are JPEG, GIF, PNG.
A GIF image is a GIF image whether animated or not. SEO crawlers don't "see" the difference; they just read the ALT text. (I think.)
=========
JPEG's are for tonal images (photos, gradients), GIFs for flat 256 colors and transparent ares. PNG-24 offers shades of transparency.
@SeawitchauthorJan 14.2013 — #It seems that the multiple frames of an animated GIF are no draw to search engine crawlers wheras image quality is now, and the reduced palate of a GIF is a drawback, so I've gone back to a J.PEG for my home page..
@auntniniJan 14.2013 — #Really??? Can you give some reference links to back up that statement? It does not seem likely that SEO or anybody would make that distinction.
One thing for sure, you need ALT="alternate text" attribute of IMG tag. And that's what SEO crawlers "see."
@Steve_SmithJan 15.2013 — #Jpegs and gifs are the most commonly used graphic formats on the web. Each has it's unique advantages and disadvantages. The material covered in this article will help you decide which format is more appropriate for your images. A general rule of thumb; use gifs for illustrations, clip art, and images with large areas of flat color, use jpgs for photographs and images with continuos tones.