javascript当中onblur和onfocus用法

例 1.1 onblur和onfocus
马克-to-win：onblur失去焦点和onfocus得到焦点事件。



<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML>
<head>
    <meta http-equiv="content-type" content="text/html; charset=utf-8"/>
<SCRIPT LANGUAGE="JavaScript">
    <!--
    function check(a)
    {
        var username = a.value;
        if (username == "")
        {
            /*String.fontcolor() (Method)
    Encapsulates the string within an <FONT COLOR="..."> tag context.*/
            document.getElementById("error").innerHTML = "用户名不能为空！".fontcolor("red");
        }
    }
    function rese()
    {
        document.getElementById("error").innerHTML = "";
    }
    //-->
</SCRIPT>
</HEAD>
<BODY onload="document.getElementById('u').focus()">
we can not leave the following input blank.
用户名：<INPUT id="u" TYPE="text" NAME="" onblur="check(this)" onfocus="rese()"><span id="error"></span><BR>
</BODY>
</HTML>