Google has added some new options in YouTube that makes it easy for you to embed YouTube videos that are available in Widescreen 16:9 format. You can access these new options by clicking the customize icon next to the embed code as in the screenshot.
Here you can see a sample widescreen video clip from YouTube embedded in the blog.
Related: Embed YouTube Videos in PowerPoint
New embed options for regular 4:3 videos
And for regular videos on YouTube that aren’t available in the Widescreen format, you are no longer limited to the default 425×355 dimensions for embedding as there’re a couple of new player size choices available like 640×505 and 320×265. Hat tip Stagueve.