Add a video you like to your blog from either Youtube or Google Video.
From Youtube:
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To embed this video right onto your blog copy the code (Ctrl+C) in this embed box.
From Google Video:
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When you click that link some more links show up. Click on the one that says "Embed HTML".
If you want to embed this video right onto your blog, copy the code (Ctrl+C) in the embed box.