Stretch YouTube Video To Fit Browser Window

Fit a YouTube video in the browser window as follows:

Normal YouTube Video URL is https://www.youtube.com/watch?v=grItaOxuyTE&t

To watch in a re-sizable window without switching to Full Screen rewrite the above URLas follows:

https://www.youtube.com/v/grItaOxuyTE&t

Append your YouTube video ID to www.youtube.com/v/VIDEO_ID to display a re-sizeable browser window.

In other words replace /watch?v= with /v/ in the normal URL