Add float:left;
to #under_post
and #post_info
#under_post {
margin: 0;
padding: 0;
width: 600px;
border: 1px solid black;
float: left;
}
#post_info {
margin: 0;
padding: 0;
width: 400px;
float: left;
}
and add float:right;margin-top:25px;
to div#download_button
div#download_button {
width: 100px;
float: right;
margin-top: 25px;
}
This is how it looks