Yes, that would be the case if you give everything a hard position.
There are some tricks though.
I'm just assuming that you want to center your layout.
To do this you will have to place all of your content divs in a main div which you center with CSS.

Code:
<html>
<head>
    <title>Example page</title>
</head>

<body>
    <div id="main_div">
        <div id="header">Header image</div>
        <div id="content">Page content</div>
    </div>
</body>
</html>
And the CSS would be something like this:

Code:
#main_div {
    position: relative;
    margin: auto;

    width: 800px;
    height: 700px;
}

#header {
    position: absolute;

    top: 0px;
    left: 0px;
    width: 800px;
    height: 100px;
}

#content{
    position: absolute;

    top: 100px;
    left: 0px;
    width: 800px;
    height: 600px;
}

The above example would create a simple page with a box of 800x700 which is always centered horizontally in the page.
This example is not centered vertically.
It is possible to create vertically centered layouts but it is a pain in the butt to do so.
I'd rather suggest you make a layout which centers horizontally and uses the full vertical page, this is a lot easier to code.