3. inclusionBoxes (view source) の方法であれば、スマートかつ安全にボックスを包含できるようになるのではないか、という提案です。
動作確認ブラウザ: IE6, 7 / Fx 2 / Opera 9.5 / NN 7.1 / Safari 2, 3
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>inclusionBoxes - tshinobu.com</title>
<style type="text/css">
.layoutbox{
background: #EEE;
}
.innerA{
float: left;
width: 200px;
height: 1000px;
background: #F99;
}
.innerB{
float: left;
width: 600px;
height: 500px;
background: #99F;
}
</style>
</head>
<body>
<div class="layoutbox">
<div class="innerA">innerA</div>
<div class="innerB">innerB</div>
</div>
<div class="layoutbox">
<div class="innerA">innerA</div>
<div class="innerB">innerB</div>
</div>
</body>
</html>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>inclusionBoxes - tshinobu.com</title>
<style type="text/css">
.layoutbox{
background: #EEE;
}
.innerA{
float: left;
width: 200px;
height: 1000px;
background: #F99;
}
.innerB{
float: left;
width: 600px;
height: 500px;
background: #99F;
}
/*----- clearfix scheme -----*/
div{
display: inline-block;
}
div:after{
height: 0;
visibility: hidden;
content: url("clearfix.gif");
display: block;
clear:both;
}
/* hide MacIE \*/
* html div {height: 1em;}
div {display: block;}
/* ini */
</style>
</head>
<body>
<div class="layoutbox">
<div class="innerA">innerA</div>
<div class="innerB">innerB</div>
</div>
<div class="layoutbox">
<div class="innerA">innerA</div>
<div class="innerB">innerB</div>
</div>
</body>
</html>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>inclusionBoxes - tshinobu.com</title>
<style type="text/css">
.layoutbox{
background: #EEE;
overflow: auto;
}
* html .layoutbox{
zoom: 1;
overflow: visible;
}
.innerA{
float: left;
width: 200px;
height: 200px;
background: #F99;
}
.innerB{
float: left;
width: 600px;
height: 50px;
background: #99F;
}
</style>
</head>
<body>
<div class="layoutbox">
<div class="innerA">innerA</div>
<div class="innerB">innerB</div>
</div>
<div class="layoutbox">
<div class="innerA">innerA</div>
<div class="innerB">innerB</div>
</div>
</body>
</html>