もうだめだ

CSS 
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" lang="ja" xml:lang="ja">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=shift_jis" />
<meta name="robots" content="index, follow" />
<meta name="Keywords" content="にーにー" />
<meta name="Description" content="にゃーにゃー。" />
<title>かわいいこねこ</title>

<link href="./style/base.css" rel="stylesheet" type="text/css" media="screen" />
</head>
<body>
<div id="container">
  <div id="header">
header
 </div>
  <div id="nav"><p class="path">ホーム&gt;</p><p class="date">最終更新日時：08年7月25日(金)18時40分</p></div>

    <!-- -------left area--------- -->
	<div id="left">
	left
	</div>
    <!-- -------center area --------- -->
  <div id="main">
	<div id="center">center</div>
	<div id="right">right</div>
　</div>
  <div id="footer">footer</div>
</div>
</body>
</html>
base.css
/* base style */

* {
	background: transparent;
	font-size: 100%;
	margin: 0;
	padding: 0;
}
body {
	color: #333;
	font-size: 80%;
}
img {
	vertical-align: middle;
	border: none;
}
a {
	color:#FF6633;
}
a:hover {
	color:#FF6600;
}
.clears {
	clear: both;
}

/* ----コンテナ部---------------------- */

div#container{
width:850px;
height:auto;
border:#333 solid 1px;
}
div#nav{
background:url(../images/bk_nav.gif) no-repeat;
height:19px;
}
div#header {
	height:100px;
	border:1px;
}

div#main{
width:81%;
	border:#333 solid 1px;background-color:red;
	float:right;
}

div#left{
	border:#333 solid 1px;background-color:blue;
	float:left;
	height:111px;
	width:223px;
}
div#center{
	border:#333 solid 1px;background-color:green;
	padding-top:5px;
	float:left;
	height:auto;
	width:461px;
	border:#333 solid 1px;
}
div#right {
	float:right;
	height:auto;
	width:18%;
	border:#333 solid 1px;background-color:yellow;
}
div#footer{
width:100%;
	clear:both;
border:#333 solid 1px;
}

FFoxでみるとleftくんがいなくなります。なぜ！なぜ！