Some ad sizes are now seen less often because they do not perform well or do not fit modern devices. For example, small banner sizes like 234x60 or 120x240 don’t give much space to display your message. These older formats also don’t look great on mobile screens, which is where a lot of people are seeing ads now. Instead, most advertisers use sizes like 300x250, 728x90, or 160x600 because they show better results and are supported by more websites. Google and other networks often give a list of top-performing sizes, so checking those can help. If anyone has seen newer sizes work better or worse, that would be good to share.