1. There are three main rules for images on websites: save images in the correct format (JPEG, GIF, or PNG), save images at the right size by resizing in a photo editor, and always measure images in pixels. 2. JPEG is best for photos with many colors, GIF is best for logos and animations with sharp lines and solid colors, and PNG is similar to GIF but supports transparency. 3. Images can be inserted into a website by saving them in an image folder and using HTML code with the <img> tag to specify the source and alt text, or with <figure> tags to add a caption.