<link rel="apple-touch-startup-image"/>

The <link rel="apple-touch-startup-image"/> tag in HTML 5

The <link rel="apple-touch-startup-image"/> meta tag specifies a startup image, which is an image that is displayed while an offline web application is being launched on the mobile device. For the iPhone and iPod Touch, the image must be in portrait orientation 320 pixels wide by 460 pixels high.