Every time i try to post a youtube video, a blank white area appears on screen.

I read a post of a guy who told about something removing from the url of youtube video, but please can you explain me?

Here is how it looks like:

A youtube button was added in post tools so it's easier now.
1. Take the number in your youtube file after the v= example: utR2oxOwaxk
2. highlight that number and click the red tube button above.
3. You'll have a video like the one below, use "go advanced" and preview to make sure you've got it right before posting.