Removing borders/margins on posts

Hi! I’m very new to wordpress and have messed around a bit with CSS to remove the borders on my page. I’ve been able to removed the borders of my actual page (headline image stretches all the way across) but I still have a ton of white space around my individual posts and sidebar. My website is site and I’ll paste the CSS adjustments I’ve tried below. Thanks!

#page {
	max-width: none;
}

body {
	padding: 0;
}

#page {
	margin: 0 !important;
}

#content {
	margin-left: 0;
	width: 75%;
}

#secondary {
	margin-right: 0;
}
.size-full {
display: block;
margin: 0 10px 10 px 0;
}
img {
border: none;
}
.the_content img {
-moz-background-clip:border;
-moz-background-inline-policy:continuous;
-moz-background-origin:padding;
background:white none repeat scroll 0 0;
border:1px solid #DDDDDD;
padding:3px;
}

change to:

.the_content img {
-moz-background-clip:border;
-moz-background-inline-policy:continuous;
-moz-background-origin:padding;
background:white none repeat scroll 0 0;
}
.post_image img {
padding:0;
background-color:#fff;
border:none