title: hidden folders in Internet
body: <p>very often in Internet I see links like this:</p>
  
  <pre><code>www.abcde.com/~main/material/hello
  </code></pre>
  
  <p>and this part <code>~main/material/hello</code> is grey, if I remove <code>hello</code> I receive access forbidden, can somebody explain, what is this system, and is it possible receive access?</p>