How do I find the user who logged in?

 
Good evening ASP programmers,
I have built a website which is accessible to everyone.  There is one section of the website which is only accessible to a few users with User Names and Passwords.  I built the secure area by modifying the web.config file; it now includes the following:
<authentication mode="Forms" >
  <forms>
    <credentials passwordFormat="Clear">
      <user name="userName1" password="pswd1" />
      <user name="userName2" password="pswd2" />
      <user name="userName3" password="pswd3" />
    </credentials>
  </forms>
</authentication>
The secure pages are all within a folder whose name begins with an underscore, i.e. _secureWebPage ...