header help

Hi, everyone,

I am looking to replace by top banner on wordpress with an image. The banner’s width is 860px. I have an image that is that length that I want to use, but the height is larger than that of my header.

My question is if its possible to change the height of my header? How can this be achieved? I am a novice in css.

There appears to be no line of code for height:

This is the code under style.css:

#container {
background: #ffffff;
width: 860px;
text-align: left;
margin: 20px auto 20px auto;
border: 1px solid #cccccc;
overflow: hidden;
}
#header {
background-color:#223546;
padding: 25px 35px 75px 35px;
text-align: left;
}
#header h2 {
color: #ffffff;
font-size: 30px;
font-family: Helvetica, Arial, Verdana, Sans-Serif;
font-weight: bold;
margin: 0px;
}

#header h2 a {
color: #ffffff;
text-decoration: none;
}

#header h2 a:hover {
color: #006699;
text-decoration: none;
}

#header h3 {
color: #ffffff;
font-size: 13px;
font-family: Georgia, Times New Roman, Sans-Serif;
text-indent: 5px;
margin: 0px;
}

I added a line for height, but it didn’t work.