文本输入框默认内容实现一

结构

<input onfocus="getfocus()" onblur="outfocus()" name="username" type="text" value="输入关键字" class="txt01" />

样式

.txt01 {
 color: #999999;
 border: 1px solid #999999;
}
.txt02 {
 color: #3366FF;
 border: 1px solid #3366FF;
}
.txt03{
 border:1px solid #999999;
 color: #3366FF;
}

行为

<script type="text/javascript">
    function getfocus() {
        if (username.value == '输入关键字') {
            username.value = '';
        }
        username.className = 'txt02';
    }
    function outfocus() {
        if (username.value == '') {
            username.value = '输入关键字';
            username.className = 'txt01';
        } else {
            username.className = 'txt03';
        }
    }
</script>