Web page shortcut file (.url or .webloc file extension) is required to use the web page as digital signage content.
.url file is simpler than .webloc file and its format is as follows.
[InternetShortcut] URL=<YOUR URL HERE>
You can change <YOUR URL HERE> to a URL you like.
Here is an example file. You can put the example file on your Google Drive folder and confirm how your screen shows a Google search page.
Because web page content generally requires separate settings (width / height / refresh interval), the example file is named with "_ww1280_wh720_wr10". In the feature page, you can find separate settings for web pages.