I've written this real basic site t... in iWeb.
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I'm not too familiar with iWeb. You should probably post some details on which features you're trying to use.
At a guess, you're using a template, and the canned blog abilities. It appears to require some specific PHP server side abilitiy.
You're hosting at a free webspace, and they may not have PHP installed (or not the required version or settings).
Since you own the domain, I'd recommend getting some cheap hosting, and select the hosting provider based on some forum reading or stated support for iWeb.