You can reduce the file size of photos you add to your websites, which helps your website publish faster and helps photos display and download faster for your visitors.
For visitor downloads
Photos you add to a Photos template are imported full size and “downsampled” (reduced in size) automatically when you publish your website. You can still modify their download size (the size of images that visitors download from your site) to allow for faster downloading, for higher-quality images, and so on.
Open a photos page by clicking it in the sidebar on the left of the iWeb window.
If the Photos inspector isn’t open, click Inspector in the toolbar at the bottom of the iWeb window, and then click the Photos button.
In the Photos pane, choose an option from the Photo Download Size pop-up menu.
For very large imported images
If you’re using very large, high-quality JPEG images in your website, you can choose iWeb > Preferences and select “Optimize images on import.”
This setting reduces the size of imported images by up to 60 percent so that they don’t take up as much space in your Domain file, where your website files are stored on your computer. The larger the images on your website, the more space these files takes up on your hard drive.