What you tried didn't work, regardless. Try using FEN tags as he suggested. Or, for the tag impaired, click on the "Insert board from FEN button."
But if you're talking about an offsite forum (the stoner one that was posted?), then obviously, this isn't going to work and you need to come up with your own solution.
It looks like the FEN tags generate some javascript to generate the board. For instance, the board DemonSin posted above came out in my HTML like this:
RenderBoard(12,'rnbq3r/p1ppkpQp/1p1b1n2/4p3/8/3P1N2/PPP1PPPP/RNB1KB1R w KQ - 1 6' );
You can probably find a way to source in their javascript and use their renderboard function without too much trouble. Maybe it'll even work. And maybe it won't break their intellectual rights (call me a skeptic).
Looks like it comes in from this script:
http://www.redhotpawn.com//jscript/rhplib_017_ob.js