I'm not really sure how. Most web pages don't have dynamic lighting. I suspect that the amount of information to encode the flat image plus the normal map is go

I'm not really sure how. Most web pages don't have dynamic lighting. I suspect that the amount of information to encode the flat image plus the normal map is going to be more than the amount of information to encode the pre-rendered effect. Now, if you were planning on doing some kind of dyanmic lighting in a web page, then sure, this would help. But I can't think of much use for dynamic lighting outside of games or other physical simulations, which is likely overkill for most webapps.