Jetpack Gallery – full width?

Hi!

I did make a gallery with Jetpack. For some reason it does not use the full width…
have a look here: http://www.geri.at/wordpress/?p=813

My Custom CSS looks like this:
(Collected some code snippets – not sure what every one is doing in real…)

#header {
display: none;
}

#access a {
padding-right: 22px;
} 

#slider .entry-title a {
display:none;
}

#site-title img {
margin: 0px;
}

#site-title {
margin:0;
line-height:0;
float:left;
}

#access ul {
height: 40px;
}

#social-media-icons {
display:none;
float:none;
margin-top:0;
}

#header input#s {
display: none;
}

/* Galerie Vorschau stretched auf max width */
.post-gallery-item img {
	display:block;
	width:100%;
	float:left;
}

#sidebar .onecol {
    border:#ccc 1px solid;
margin-top: 20px;
}

.widget-area li {
	padding:7px 0;
	margin:0;
	border-bottom:#ccc 1px solid;
	line-height:1.62em;
}

Any idea?

Thnx!

Greetings
Geri