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 == “”)
{
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()”>
