Of course, you put a site live, and you run into trouble. Turns out the widget I chose for displaying my Flickr photostream uses the file_get_contents() PHP function to fetch the contents of the Flickr feed. Whether this is at all possible is governed by the PHP setting allow_url_fopen, and my hosting provider has it turned off. This is not at all uncommon, because when a script is not coded carefully, it would be possible to load a remote file into a script that was only ever intended to load local files. Scary.