#main{
display:table;
border-collapse:collapse;
}
#nav{
display:table-cell;
width:180px;
background-color:#e7dbcd;
}
#extras{
display:table-cell;
width:180px;
padding-left:10px;
border-right:1pxdotted#d7ad7b;
}
#content{
display:table-cell;
width:380px;
padding-left:10px;
}
<!DOCTYPEhtmlPUBLIC"-//W3C//DTDXHTML1.0Strict//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<htmlxmlnshtmlxmlns=http://www.w3.org/1999/xhtml
lang="en-US">
<head>
?HTMLheadcontent…
</head>
<body>
<div id="wrapper">
<div id="header"></div>
<div id="main">
<span style="white-space:pre"> </span><div id="nav">
<span style="white-space:pre"> </span>?navigationcolumncontent…
<span style="white-space:pre"> </span></div>
<span style="white-space:pre"> </span><div id="extras">
<span style="white-space:pre"> </span>?newsheadlinescolumncontent…
<span style="white-space:pre"> </span></div>
<span style="white-space:pre"> </span><div id="content">
<span style="white-space:pre"> </span>?mainarticlecontent…
<span style="white-space:pre"> </span></div>
</div>
</div>
</body>
给main上使用display:table 在nav extras content上使用display:table-cell成功实现三栏等高布局!