Hulu videos can be a bit tricky to embed compared to content from typical streaming media sites. This is because the uniform resource locator (URL) visible in your browser cannot be used to determine the source URL due to the fact that Hulu source URL's are encrypted in their embed code.
To emebed Hulu videos you must manually extract the source URL from the embed code provided by Hulu before you copy and paste it into the video url text box when making or editing a post. You can find source URL's by clicking on the "embed" icon while watching a Hulu video and then extracting the part of the code circled in green below.
If a video is flagged by Hulu as mature then you must sign up for a Hulu membership before you can view of find the embed code from that video.