HTML三列布局无法正确显示

Question

我是HTML的新手，我正在尝试建立一个三柱流体网站。使用我在网上找到的以下代码，我应该得到这个：

http://s29.postimg.org/ulf8ccntz/Screen_Shot_2014_02_22_at_11_45_05_PM.png

然而，我实际上得到的是：

http://s12.postimg.org/uu5lw9qod/Screen_Shot_2014_02_22_at_11_43_07_PM.png

有谁知道发生了什么事？谢谢大家!!

<div id="container">
<div id="header">
    <h1>
        Site name
    </h1>
</div>
<div id="navigation">
    <ul>
        <li><a href="#">Home</a></li>
        <li><a href="#">About</a></li>
        <li><a href="#">Services</a></li>
        <li><a href="#">Contact us</a></li>
    </ul>
</div>
<div id="content-container1">
    <div id="content-container2">
        <div id="section-navigation">
            <ul>
                <li><a href="#">Section page 1</a></li>
                <li><a href="#">Section page 2</a></li>
                <li><a href="#">Section page 3</a></li>
                <li><a href="#">Section page 4</a></li>
            </ul>
        </div>
        <div id="content">
            <h2>
                Page heading
            </h2>
            <p>
                Lorem ipsum dolor sit amet consect etuer adipi scing elit sed diam nonummy nibh euismod tinunt ut laoreet dolore magna aliquam erat volut. Ut wisi enim ad minim veniam, quis nostrud exerci tation ullamcorper suscipit lobortis nisl ut aliquip ex ea commodo consequat. Duis autem vel eum iriure dolor in hendrerit in vulputate velit esse molestie consequat, vel illum dolore eu feugiat nulla facilisis at vero eros et accumsan et iusto odio dignissim qui blandit praesent luptatum zzril delenit augue duis dolore te feugait nulla facilisi. 
            </p>
            <p>
                Ut wisi enim ad minim veniam, quis nostrud exerci tation ullamcorper suscipit lobortis nisl ut aliquip ex ea commodo consequat. Duis autem vel eum iriure dolor in hendrerit in vulputate velit esse molestie consequat, vel illum dolore eu feugiat nulla facilisis at vero eros et accumsan et iusto odio dignissim qui blandit praesent luptatum zzril delenit augue duis dolore te feugait nulla facilisi. Lorem ipsum dolor sit amet, consectetuer adipiscing elit, sed diam nonummy nibh euismod tincidunt ut laoreet dolore magna aliquam erat volutpat. 
            </p>
            <p>
                Duis autem vel eum iriure dolor in hendrerit in vulputate velit esse molestie consequat, vel illum dolore eu feugiat nulla facilisis at vero eros et accumsan et iusto odio dignissim qui blandit praesent luptatum zzril delenit augue duis dolore te feugait nulla facilisi. Lorem ipsum dolor sit amet, consectetuer adipiscing elit, sed diam nonummy nibh euismod tincidunt ut laoreet dolore magna aliquam erat volutpat. Ut wisi enim ad minim veniam, quis nostrud exerci tation ullamcorper suscipit lobortis nisl ut aliquip ex ea commodo consequat. 
            </p>
        </div>
        <div id="aside">
            <h3>
                Aside heading
            </h3>
            <p>
                Duis autem vel eum iriure dolor in hendrerit in vulputate velit esse molestie consequat, vel illum dolore eu feugiat nulla facilisis at vero eros et accumsan.
            </p>
        </div>
        <div id="footer">
            Copyright © Site name, 20XX
        </div>
    </div>
</div>