What is the best file format to save my images in for the websites and my banner?

PRESSERO > *Pressero FAQs
We recommend png format. If the image is being created in Photoshop, you should also use the "Save for web and devices" option instead of just hitting "Save as" and choosing png. This will do the best compression with the best quality that most browsers prefer. A great benefit of png is that it saves transparency, which is nice for logos and images that are against a dark background.