Make it fluid

This seems to work as a fluid layout. FYI, the background image (the beige part with the shadows) has been eliminated.
In styles.css, change the body, #header and #wrapper styles to this:

body {
margin: 0;
padding: 0;
color: #696969;
font-family: Arial, Verdana, Geneva, Helvetica, sans-serif;
font-size: 73%;
background-color: #FFF;
}

#header {
position:relative;
/* height:116px; */
overflow:hidden;
background-color: #C5E18A;
background-image: url(img/header_bg.png);
background-repeat: repeat-x;
}

#wrapper {
width:100%;
padding:0;
text-align:left;
margin-top: 0px;
margin-right: auto;
margin-bottom: 4px;
margin-left: auto;
}

Just noticed that your question is about v5, and I'm using v6.2. But it should work the same, since only the CSS is changing.

Hello Buffer2k. Did you test it by now?

I do not plan to make a fluid version for now. Probably in next releases