Under What type of file do you want?, select an interlacing option to determine how the image is displayed as it downloads:
Non-interlaced: The image downloads one line at a time, starting from the top.
Interlaced: The image is displayed incrementally in several passes, and detail is added each time. Use this option with larger images so that the viewer can get an idea of how the image looks while waiting for it to download.
Choose a version for the file. Choose the Version 89a option to save transparency information. It is selected automatically if the image contains transparent pixels. Version 87a is available only if the image does not contain a transparency.
Previewing images in a Web Browser