360水动力吸脂效果:有关网页程序

<input type="submit" name="rulesubmit" value="下一页" style="height: 23px" >
<input type="button" name="return" value="关闭" style="height: 23px" onClick="javascript:history.go(-1);">
<br>
<br>
</center></td>
</tr>
</table></td>
</tr>
</table>
</form>
<script language="JavaScript">
var secs = 30;
var wait = secs * 1000;
document.bbrules.rulesubmit.value = "下一页(" + secs + ")";
document.bbrules.rulesubmit.disabled = true;
for(i = 1; i <= secs; i++) {
window.setTimeout("update(" + i + ")", i * 1000);
}
window.setTimeout("timer()", wait);
function update(num, value) {
if(num == (wait/1000)) {
document.bbrules.rulesubmit.value = "下一页";
} else {
printnr = (wait / 1000)-num;
document.bbrules.rulesubmit.value = "下一页(" + printnr + ")";
}
}
function timer() {
document.bbrules.rulesubmit.disabled = false;
document.bbrules.rulesubmit.value = "下一页";
}
</script>
</body>
</html>
程序大概是什么意思..谢谢
主要是程序中的命令..时间等等 我想了解下什么意思.这个我从网页上拽下来的