Dithering is done once (not every request) so not a problem, I will add "once" gzip compression to images at some point but only when the load on my blog increases to the point of breaking bandwidth. I suspect CPU will falter first so no point worrying really!

I don't understand, so maybe we're talking past each other. JPEG compression is only done once as well.

Also, gzipping a GIF is actually likely to make it bigger!

Ok, I thought you meant HTTP compression, but yeah it makes it bigger! jpeg is not interesting to begin with because of artifacts. The dithering is a style, all-in-all my choice had very little to do with actual size savings... it's also simpler = can be displayed on monochrome displays, the code to make it and render it is simpler. etc. etc. Sure in pure bandwidth savings you'll win every day of the week, but in style? Life without art is meaningless for humans. Dithering is minimalism of expression!