title: How to tell when a web page has changed by x% in VB.net?
body: <p>I'm trying to write a little utility which will check periodically and tell me if/when a web page's (could be any URL) content has changed. I've read the other postings but they don't really answer my question (as far as I can tell).</p>
  
  <p>I know for static pages there is a last-modified header. However, what about dynamic pages? I got Oli's comment that storing a hash of the contents works but that's not really idea because the page might simply have a time stamp on it (the date-time that the page was produced). Clearly, in this case, the content would be different on every single request even though nothing significant has changed.</p>
  
  <p>So, now I'm thinking to tie it to a percentage of 'changedness.' Something like, more than 5% changed will cause the 'changed' logic to run.</p>
  
  <p>I'd love to hear any ideas on how I can reliably tell when a page has changed, in a meaningful way.</p>