We were wondering if someone can help us

We have been authoring an education blog "The Imaginers Chronicles" and each of our articles contain a flash video. Unfortunately flash is no longer support in html5 and many of the new mobile browsers.

Therefore we are trying to reformat them to meet the requirement of these new browsers.

We have already converted most of the 150 videos on our site (we have been posting two articles a month along with videos since 2007) to the following formats. mp4, webm, ogg and installed a script below I which we obtained on line.

However we see an error message "invalid source" (Please visit << http://www.theimagineershome.com/blog/?p=2519 >> to view error" when we attempt to open it on the web.

Could someone please help us to understand what we are doing incorrectly and help us to get our site up and running again.
Thank you
Jeff and friends

<table border="1" width="200" bgcolor="#333333" align="right">
<tbody>
<tr>
<td>
<video id="myvideo" controls="controls" autoplay="autoplay" poster="images/what_is_time.jpg">
<source src="http://www.theimagineershome.com/blog/video/10_what_is_time/10_what_is_time.mp4" type="video/mp4" >
<source src="http://www.theimagineershome.com/blog/video/10_what_is_time/10_what_is_time.webm" type="video/webm">
<source src="http://www.theimagineershome.com/blog/video/10_what_is_time/10_what_is_time.ogg" type="video/ogg">
</video></td>
</tr>
<tr>
<td>
<p align="center"><span style="font-family: arial; color: #0080ff; font-size: small"><a href="http://www.youtube.com/watch?v=sfN-7HczmOU"><strong><span style="color: #0080ff; font-size: small"><font size="3">What is time</font></span></strong></a></span></p>
</td>
</tr>
</tbody>
</table>