Interlacing Gifs:
samples on local drive>>>
Interlaced images gradually load in showing increased resolution so you can see something loading while the page loads.
Photoshop 5.0-5.5:
1. Open an image in Photoshop.
2. Choose File>Export>GIF89a Export.
3. Select the interlaced option in the dialog box.
Photoshop 6.0 and up:
1. Open an image in Photoshop.
2. Choose File>Save for Web.
3. Select the interlaced option in the dialog box.