[calorie]

The HTML from your site has the following:

	<div class="page" style="width:90%; text-align:left">

This is coming from the spacer_open template:

	<div class="page" style="width:$stylevar[outerdivwidth]; text-align:$stylevar[left]">

That is, your $stylevar[outerdivwidth] is set to 90 percent, making the posts narrower than the rest of the page. In order to get this corrected for your skin, edit the spacer_open template, replacing the following:

width:$stylevar[outerdivwidth];

With the following:

width:100%;

That change should make it so your skin shows posts at the wider width.

Alternatively, you could try and set the Main Table Width in ACP -> Styles & Templates -> Style Manager -> StyleVars to 100% and see if that does it.