Files for Individual Pages
The images in those folders are typically PNG files and contain the images from an iWeb page cropped, resized, color-adjusted, tilted, and with the iWeb special added and the requisite transparency applied to them. (They look like you edited the original images with Photoshop by hand and saved them as PNG files.) JPEGs typically appear only for photos that you have not edited at all using iWeb. Any text elements you create using nonstandard fonts (such as Papyrus) are saved as PNG image files and stored in these folders.
There’s also the standard stylesheet used by the iWeb template that you selected when you created the page. However, don’t expect that to be the full stylesheet for the page. Each iWeb page is created with a heavily reliance on style elements. The second you open one up, you see tons of <div> tags, each with its own style elements included. I’ll discuss this more in part two of this series, but working with iWeb-generated pages outside of iWeb requires you to be comfortable using style elements.
There is also an Images folder, which can contain default elements from the iWeb templates. If you delete all the stock images, this folder is typically empty.