Whatever the browser, when bookmarking a page, its default title is the title of the page itself. This default value perfectly makes sense. However, iOS and Windows 8 let you set an “application name”. Well, technically speaking, nothing differentiates a web app from a web site, but the idea here is to make your web app sound like a native app (RealFaviconGenerator will only help you scratch the surface here).
You’ve just generated a cool Apple Touch icon for your latest web project. Everything is ready and you decide to give it a try by adding the homepage to the home screen of your iPhone. The result is okay but… you can’t remember all that black in the original icon.
The reason: iOS forbids transparent icons. And it must have listened for the Rolling Stones hit for too long because it fills the gaps with black.