title: XSS Attack on my page for testing and solving issue
body: <p>I want to test XSS locally, so I write a single HTML page and execute it by</p>
  <p><strong>../index.html?q=alert(123)</strong></p>
  <p>or</p>
  <p><strong>../index.html?q=%3Cscript%3Ealert(123)%3C/script%3E</strong></p>
  <p>but no alert shown in the output, Where is my work wrong?</p>