title: Technology behind [crawlera](http://crawlera.com)(What tools the use to download page content)
body: <p>I usually use urllib module in python to scrap data.</p>
  
  <p>Certain websites are blocking to download the page content they are throwing 404 error but the website is live.</p>
  
  <p>In such cases I use crawler proxies.</p>
  
  <p>I wonder what tools and technologies they use for blacklist the website to make this work from 404 to 200</p>
  
  <p>Could any one have idea behind it?</p>