求助一个问题，为什么功能实现不了
<html><head>
<title>无标题文档</title>
<style type="text/css">
</style>
<script type="text/javascript">
function showLength() {
var texts = document.form1.strings.value.length;
document.form2.lengths.value = texts;
}
function htm_fontcolor() {
var texts = document.form1.strings.value;
texts = texts.fontcolor("blue");
document.form2.lengths.value = texts;
}
function htm_big() {
var texts = document.form1.strings.value;
texts = text.big();
document.form2.lengths.value = texts;
}
function bigToSmall() {
var texts = document.form1.strings.value;
texts = texts.toLowerCase();
document.form2.lengths.value = texts;
}
function htm_bold() {
var texts = document.form1.strings.value;
texts = texts.bold();
document.form2.lengths.value = texts;
}
</script>
</head>
<body>
<center>
<form name="form1">
请输入内容：<br/>
<textarea name="strings" rows="5" cols="30"></textarea>
</form>
<form name="form2">
<input type="button" value="显示字符串长度" onClick="showLength()"><br/>
<input type="button" value="<big>标记" onClick="htm_big()"><br/>
<input type="button" value="全部转换为小写" onClick="bigToSmall()"><br/>
<input type="text" name="lengths" size="40"><p>
<input type="button" value="粗体显示" onClick="htm_bold()">
<input type="button" value="显示为蓝色字体" onClick="htm_fontcolor()">
</form>
</center>
</body>
</html>
为什么大写转小写功能可以实现，粗体显示和显示为蓝色字体功能实现不了呢，谢谢各位
