How to move body up on page?

Hello!

I’ve been trying for hours to figure out how to move the content in a page closer to the header. I thought it would be very simple to do, but I haven’t made any progress. I believe I need to change the top margin somewhere in the following code, and I’m hoping someone can help guide me…

Here is my site…

Thank you!

body {
/*background: #EFEFEF;*/
font-size: 15px;
}

body .grid-container {
max-width: 1100px;
}
/*.inside-article,
.sidebar .widget,
.comments-area,
.page-header,
.footer-widgets,
.paging-navigation {
background:#FFF;
}*/

.separate-containers .inside-article,
.separate-containers .widget,
.separate-containers .comments-area,
.separate-containers .page-header,
.separate-containers .paging-navigation {
padding: 40px;
}

/*.one-container .container {
background: #FFF;
}*/

h1 {
font-size: 35px;
margin-bottom: 20px;
line-height: 1.2em;
}
h2 {
font-size: 25px;
margin-bottom: 20px;
line-height: 1.2em;
}
h3 {
font-size: 20px;
margin-bottom: 20px;
line-height: 1.2em;
}

h4, h5, h6 {
margin-bottom: 20px;
}

/* Layout spacing */
.right-sidebar .site-main {
margin: 30px 30px 30px 0;
}
.left-sidebar .site-main {
margin: 30px 0 30px 30px;
}
.both-sidebars.separate-containers .site-main {
margin: 30px;
}
.both-right.separate-containers .site-main {
margin: 30px 30px 30px 0;
}
.both-left.separate-containers .site-main {
margin: 30px 0px 30px 30px;
}
.both-left .inside-left-sidebar {
margin-right: 15px;
}
.both-left .inside-right-sidebar {
margin-left: 15px;
}
.both-right .inside-left-sidebar {
margin-right: 15px;
}
.both-right .inside-right-sidebar {
margin-left: 15px;
}
.site-main {
margin: 30px 0;
}
.separate-containers .site-main > *:last-child {
margin-bottom: 0;
}
.inside-right-sidebar,
.inside-left-sidebar {
margin: 30px 0;
}
.one-container .site-main {
margin-top: 0;
margin-bottom: 0;
}
.one-container .site-content {
padding: 40px;
}
.one-container .site-main {
margin-top: 0;
margin-left: 0;
margin-right: 0;
}
.one-container.both-right .site-main,
.one-container.right-sidebar .site-main {
margin-right: 60px;
}
.one-container.both-left .site-main,
.one-container.left-sidebar .site-main {
margin-left: 60px;
}
.one-container.both-sidebars .site-main {
margin-left: 60px;
margin-right: 60px;
}
.one-container .inside-right-sidebar,
.one-container .inside-left-sidebar {
margin-top: 0;
}
.one-container .inside-article {
padding: 0 0 30px 0;
}