favicon is shortcutIcon: page.shortcutIcon = pfad/zur/datei/favicon.ico <- one single image only!
or you can do something like:
page {
headerData {
10 = TEXT
10.value = <link rel="shortcut icon" type="image/x-icon" href="/favicon.ico">
11 = TEXT
11.value = YOUR_NEXT_HEADER_DATA
}
}