If you ever need to encode videos into WebM format, you can find the codec download at WebMProject.org.
I installed the WebM QuickTime component on my MacBook Pro and able to export to WebM format.
Currently I encode a lot of my videos into MPEG4 with h.264 codec.
95014
Which download from that site did you use? There are several there.
same question.
http://www.webmproject.org/tools/#directshow-filters
http://code.google.com/p/webm/downloads/list
http://code.google.com/p/webm/downloads/detail?name=WebM%20Component%20Installer.pkg&can=2&q=