Why doesn't this uibinder page have a vertical scrollbar?

Question

I want the browser to show a vertical scrollbar when the content grows larger than the page. The content and footer disappear below the screen instead of showing a vertical scroll bar (like we see on the SO home page).

I asked a similar question earlier, but it was directed at why the page footer wouldn't expand as the content grew. I got that sorted out but now the footer moves south but a page scrollbar never shows up.

My UiBinder xml is as follows (here's a link to the file):

<g:DockLayoutPanel unit='PX' styleName="{style.shellStyles.wrap}">
<g:north size='180'>
    <g:HTMLPanel styleName='{style.shellStyles.header}'>
        <div id="login" class="{style.shellStyles.login}">
            <g:InlineLabel ui:field="loggedInUser"/>
            <g:InlineHyperlink ui:field="loginLogoutLink"/>
        </div>
        <h1><a href="/">Flash Cards Application</a></h1>
    </g:HTMLPanel>
</g:north>
<g:center>
  <g:FlowPanel>
    <g:HTMLPanel styleName='{style.shellStyles.content}'>
        <g:SimplePanel styleName='{style.shellStyles.left}' ui:field="navigationPanel" />
        <g:SimplePanel styleName='{style.shellStyles.right}' ui:field='contentPanel' />
        <div style="clear: both;" ></div>
    </g:HTMLPanel>
    <g:HTMLPanel styleName="{style.shellStyles.footer}" height="70">
        <g:Label>&copy; Copyright by Justin Robbins</g:Label>
    </g:HTMLPanel>
  </g:FlowPanel>
</g:center>

Excerpt of CSS is as follows (here's a link to the full CSS):

.wrap {
    width: 820px;
    margin: 20px auto 10px auto;
}
@sprite .header {
gwt-image: "headerImage";
background-color: #efefef;
height: 180px;
}
@sprite .content {
    gwt-image: "contentImage";
    background-color: #efefef;
    padding: 10px 40px 20px 20px;
    min-height: 500px;
}
.left {
    width: 210px;
    float: left;
}
@sprite .left h4 {
    gwt-image: "sidebarImage";
    padding: 0 0 0 10px;
    height: 50px;
    line-height: 50px;
    color: #fff;
}
.right {
    width: 530px;
    float: right;
    padding-top: 10px;
    padding-right: 60px;
}
@sprite .footer {
    gwt-image: "footerImage";
    background-color: #efefef;
    height: 70px;
    line-height: 70px;
    color: #fff;
    text-align: center;
}

*{margin:0; padding:0;}
body {
    font-family: Arial;
    font-size: 12px; 
    background: #efefef;
    color: #232323; 
    margin:0; 
    padding:0;
    line-height: 150%;
}

Answer 1

Wrap your Flowpanel in the content area with ScrollPanel and set its height. You will get the scroll