ruby mechanize模仿js

Question

我试图刮掉使用某些js的http://georgiafacts.org/manufacturers。我的代码填写三个字段值，然后发布页面。似乎我得到了相同的屏幕，所以我不能理解js代码在做什么。

以下是按钮的代码：

<a onclick="OnSubmit();" id="ctl00_ContentPlaceHolder1_btnSearch" title="Begin Search" class="gobutton" vspace="3" alternatetext="GO" href='javascript:WebForm_DoPostBackWithOptions(new WebForm_PostBackOptions("ctl00$ContentPlaceHolder1$btnSearch", "", true, "", "", false, true))'>GO</a>

这是我的小ruby程序试图进入第二页：

require 'rubygems'
require 'mechanize'
require 'logger'
page = agent.get('http://georgiafacts.org/manufacturers/')
georgia_form = page.form
georgia_form.fields[4].value = "20"
georgia_form.fields[5].value = "20000"
georgia_form.fields[0].value = 'ctl00$ContentPlaceHolder1$btnSearch'
master_page = agent.post(georgia_form)
pp master_page

所以我的问题是，我做错了什么？