Sample code for Dialog is broken
All the samples for each type of Dialog screen here: https://jqueryui.com/dialog
The main CSS file is incorrectly linked, resulting in the modal not working correctly, such as not being resizable and everything looking wrong.
The HTTP protocol is missing:
href="//code.jquery.com
<link rel="stylesheet" href="//code.jquery.com/ui/1.13.2/themes/base/jquery-ui.css">
This looks good to me on Windows with latest FF. Can you check again?
Using // is just a wildcard for both, http.// and https://.
save the source to a local file and it doesn't work:
firefox tries to load the file with file:// if opened locally
GET file://code.jquery.com/ui/1.13.2/themes/base/jquery-ui.css net::ERR_FILE_NOT_FOUND
Including this would fix the issue if the file is stored locally:
<base href="https://code.jquery.com">
But using https:// instead of // might be easier.
Thanks for the report; fixed in https://github.com/jquery/jqueryui.com/commit/7945c962eeb513a0dd28506bf2f48a3f28a7cd4f. It should be deployed soon.