title: How to pop a dialog box /iframe/Lightbox like one below above the webpage content
body: <p>How to pop a dialog box like one below /iframe above the webpage content disabling the web page content using html/css/javascript.
  eg:when you click login in IMDB
  pls do help
  Thanks in advance</p>
  
  <p><img src="https://i.stack.imgur.com/jQpoa.png" alt="enter image description here"></p>