js新手小问题：如何显示在页面停留时间

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML>
<Head>
<Meta http-equiv="content-type" content="text/html; charset=gb2312">
<Title>JavaScript计时器</Title>
<H3><Font color="blue">主题：JavaScript计时器</Font></H3>
</Head><Body>
<Form name="fm_Time" onSubmit="0">
<Font size=5 color="red"><center> 显示您停留的时间</Center></Font><P>
<HR size=3 color="blue">
现在时间：<P>
<Input type="text" name="t_spent" id="t_spent" size=7>
</Form><BR>
</HTML>
<Script language="javascript">
var time=1;
function show_secs(){
document.getElementById('t_spent').value=time+'秒';
time++;
window.setTimeout('show_secs()',1000);
}
show_secs();
</Script>