iOS lets you define a startup image. When your visitors add your web site to their home screen, this image is displayed for a short time when the home screen link is clicked.
Now you can create this image with the help of the non-interactive API. Well, "this image" actually means "these 7 images". And the HTML code is not trivial. Definitely not something you want to deal with a few hours before the release of your next web project.
Special thanks to Taylor Fausak for his great iOS startup image reference! The official Apple docs are clearly outdated.
Oh, and if you think the photo used to illustrate this post is below standards: just try to take a screenshot of an actual startup image. The image appears for a second, at most. It is awfully hard! ;)