Using ETags?
Discussion
Never heard of them, looking now. Will it help?
I don't know what you are using for hosting or caching but yes, most browsers honor ETags for cache control to improve performance by not redownloading if they already have.
Ok, so basically just some html code. Even if a few support it, will still help.
Was also thinking to compress more. I’m way too generous keeping max size at 1MB per jpg, none for png or gif…. Most people probably only need 200-500k for what this free purpose. Save uncompressed for a paid account..