title: Verify whether a string is a valid HTML tag name
body: <p>How can I find out if a string is a valid HTML tag?</p>
  
  <p>For example: a, or h1, div, or span, ... are a valid HTML tagname.
  But ar, or abc, or div2, ... are invaild.</p>
  
  <pre><code>var Str = 'strongg';
  
  if( IsValid(Str) ) {
  // do something
  }
  </code></pre>
  
  <p>Thanks.</p>
  
  <p>PS
  I think, this was not a stupid question and I found a good solution for it here (see below). But I do not know why this thread has "-3" ? Wondering!</p>