I assume you are trying to post a YouTube video here at TS.net ...
using the supplied format of - {youtube=425,350]videoref[/youtube}
and then trying to post will result in an error because you did not post a comment (or message), just a YouTube video embedded reference. Either supply a comment, such as ...
This video really sucks ...
{youtube=425,350]videoref[/youtube}
OR if I do not wish to post a comment along with the video, I will simply add a "dot" as my message ...
.
{youtube=425,350]videoref[/youtube}
PS - the { } marks are not required, and should be replaced with [ ] marks, I had to add them in order for you to see what to type instead of TS software interpreting my post as an actual video embed.
If you really meant posting a video on YouTube, then I will guess its a similar situation - add a comment before hitting "post".