你已经正确地做了，你只需要清除你的浮动。 简单的添加

overflow: auto; 

到容器类。

最简单的解决方案是用3列组成一个表，并将该表居中。

html:

 <div id="cont">
        <table class="aa">
            <tr>
                <td>
                    <div id="left">
                        <h3 class="hh">Content1</h3>
                        </div>
                    </td>
                <td>
                    <div id="center">
                        <h3 class="hh">Content2</h3>
                        </div>
                 </td>
                <td>
                    <div id="right"><h3 class="hh">Content3</h3>
                        </div>
                </td>
            </tr>
        </table>
    </div>

css:

#cont 
{
  margin: 0px auto;    
  padding: 10px 10px;
}

#left
{    
  width: 200px;
  height: 160px;
  border: 5px solid #fff;
}

#center
{
  width: 200px;
  height: 160px;
  border: 5px solid #fff;
}

#right
{
  width: 200px;
  height: 160px;
  border: 5px solid #fff;
}

以下是当我用图像作为中心元素时，我必须对接受的答案做出的更改:

确保图像包含在div中(在本例中是#center)。如果不是，你将不得不设置显示为block，它似乎是相对于浮动元素之间的空间居中。 确保设置图像和它的容器的大小: #{中心 保证金:0自动; ｝ #center， #center > img { 宽度:100 px; 高度:汽车; ｝

可能的答案，如果你想保持HTML的顺序而不使用flex。

HTML

<div class="a">
  <div class="c">
    the 
  </div>
  <div class="c e">
    jai ho 
  </div>
  <div class="c d">
    watsup
  </div>
</div>

CSS

.a {
  width: 500px;
  margin: 0 auto;
  border: 1px solid red;
  position: relative;
  display: table;
}

.c {
  display: table-cell;
  width:33%;
}

.d {
  text-align: right;
}

.e {
  position: absolute;
  left: 50%;
  display: inline;
  width: auto;
  transform: translateX(-50%);
}

码笔链接

如果你不想改变你的HTML结构，你也可以添加text-align: center;到包装器元素和一个display: inline-block;到居中的元素。

#container {
    width:100%;
    text-align:center;
}

#left {
    float:left;
    width:100px;
}

#center {
    display: inline-block;
    margin:0 auto;
    width:100px;
}

#right {
    float:right;
    width:100px;
}

现场演示:http://jsfiddle.net/CH9K8/

我喜欢我的杠铃紧而有活力。这是css3和HTML 5

First, setting the Width to 100px is limiting. Don't do it. Second, setting the container's width to 100% will work ok, until were talking about it being a header/footer bar for the whole app, like a navigation or credits/copyright bar. Use right: 0; instead for that scenario. You are using id's (hash #container, #left, etc) instead of classes (.container, .left, etc), which is fine, unless you want to repeat your style pattern elsewhere in your code. I'd consider using classes instead. For HTML, no need to swap order for: left, center, & right. display: inline-block; fixes this, returning your code to something cleaner and logically in order again. Lastly, you need to clear the floats all up so that it doesn't mess with future <div>. You do this with the clear: both;

总结:

HTML:

<div class="container">
  <div class="left"></div>
  <div class="center"></div>
  <div class="right"></div>
  <div class="clear"></div>
</div>

CSS:

.container {right: 0; text-align: center;}

.container .left, .container .center, .container .right { display: inline-block; }

.container .left { float: left; }
.container .center { margin: 0 auto; }
.container .right { float: right; }
.clear { clear: both; }

如果使用HAML和SASS，则有加分项;)

HAML:

.container
  .left
  .center
  .right
  .clear

萨斯:

.container {
  right: 0;
  text-align: center;

  .left, .center, .right { display: inline-block; }

  .left { float: left; }
  .center { margin: 0 auto; }
  .right { float: right; }
  .clear { clear: both; }
}