WebM with alpha/transparency???

As FLV is a dying format and often not supported, I found the plugin for WebM for Premiere.  Does anyone know if WebM supports alpha/transparency?  If so, how is that done?  If not, what are my alternatives when in AME, PP or AAE?  This is for a website, so of course, codec compatibility issues aside, the Animation and CineForm render files that are much too large anyway.  I'm surprised that there's so little information about this.  And whatever info I have found has lead me SMACK into a brick wall.  

I installed an earlier version of After Effects to output a FLV for the webmaster, but that takes me back to the first point I made in this post.

Please help!  Thx!

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EDITED POST TO UPDATE: 

I worked around this by giving the webmaster an AVI with alpha, 480x720, rendered out of PP.  But I'm curious how long before someone has a solution, or a better alternative to my AVI.