Input文本框随着输入内容多少自动延伸有-bug

<!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">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>无标题文档</title>
<script language="javascript">
function checkLength(which) {
var oTextCount = document.getElementById("char"); 
iCount = which.value.replace(/[^u0000-u00ff]/g,"aa");
oTextCount.innerHTML = "<font color=#FF0000>"+ iCount.length+"</font>";
which.style.border = '1px dotted #FF0000';
which.size=iCount.length+2;
}
</script>
<style type="text/css">
.lkbnrcdvarea {
    max-width: 211px;
    min-width: 211px;

    height: 38px;
    border: 1px solid #000;
    overflow-y: hidden;
    *max-width: 201px;
    *min-width: 201px;
}
</style>
</head>
<body>
<input name="words" size="2" onkeyup="checkLength(this)"/>
<span id="char">0</span>个字符
<textarea name="" id="" cols="30" rows="10" onpropertychange="this.style.height = this.scrollHeight + 'px';" oninput="this.style.height = this.scrollHeight + 'px';" class="lkbnrcdvarea"></textarea>
<textarea name="textarea" id="textarea" style='overflow-y: hidden;height:20px' onpropertychange="this.style.height = this.scrollHeight + 'px';" oninput="this.style.height = this.scrollHeight + 'px';"></textarea>
</body>
</html>
删除时输入的字时出现问题