Tried everything to remove white space below header

Hello,

I have read so many of these support forums to get this problem fixed. I am using the utility theme, and have tried changed the margins to zero (0).

The header dimensions are 1000px width, 300px height – changed through config_variables.php.
The style.css header code is:
.header {
width: 100%;
margin-bottom: 0px;
float: center;
}
.header .head_link {
padding:0px 0;
overflow:hidden;
background:#4e4e4e;
color:#fff;
font-size:0px
}
.header .head_link p { }
.header .head_link p.best_pic {
width:100%;
text-align:center;
}
.header .head_link p span a {
padding:0 0px;
color:#fff;
}
.header .logo_cont {
padding:0px 0;
width:100%;
float:left;
}
.header .logo_cont .logo {
padding:0px 0 -100px 0px;
font-size:0px;
font-weight:bold;
color:#333333;
}
I am an intermediate WP user, and would really appreciate some help with this.