Fun fact: sending each image only once in a really big size but with brutal compression is the overall most efficient method. Like 2560×2560 at 30 to 50% jpeg.

I have a webpage, and all I can do is add code, not remove or change existing code.So I have used CSS to modify/remove parts I don't need, and thats worked fine.However there is a large banner at ...

What can't you do with CSS? We're not sure anymore. The little web standard that could seems to be capable of doing just about anything these days, including rendering a life-like image of an iPhone.