Youtube Videos have gone widescreen and Stereo HQ. If you use the usual embed code, a widescreen video will appear in default size and not widescreen. However, now Youtube offer lot of customization options ‘size-wise’ to embed Youtube videos.
To get started look for a small wheel icon on the right of embed code text box. Click on this icon to see more options. Now, you can click on boxes with different dimension to generate respective embed code.
You can select among dimensions like: 425X264, 480X295, 560X345 and 640X385 (widescreen). You can also select options like ‘include related videos’ and show border. Now you can embed Youtube videos in size that fits you best through ‘customization’ options – no need for manual code editing to change size of Youtube video display, neat! [ Embed Videos without plugin in WP ]