How does the "IE6 no more" code work?

Question

There are code samples on the IE6 No More website, such as this one:

<!--[if lt IE 7]>
<div style='border: 1px solid #F7941D; background: #FEEFDA; text-align: center; clear: both; height: 75px; position: relative;'>
  <div style='position: absolute; right: 3px; top: 3px; font-family: courier new; font-weight: bold;'><a href='#' onclick='javascript:this.parentNode.parentNode.style.display="none"; return false;'><img src='http://www.ie6nomore.com/files/theme/ie6nomore-cornerx.jpg' style='border: none;' alt='Close this notice'/></a></div>
  <div style='width: 640px; margin: 0 auto; text-align: left; padding: 0; overflow: hidden; color: black;'>
    <div style='width: 75px; float: left;'><img src='http://www.ie6nomore.com/files/theme/ie6nomore-warning.jpg' alt='Warning!'/></div>
    <div style='width: 275px; float: left; font-family: Arial, sans-serif;'>
      <div style='font-size: 14px; font-weight: bold; margin-top: 12px;'>You are using an outdated browser</div>
      <div style='font-size: 12px; margin-top: 6px; line-height: 12px;'>For a better experience using this site, please upgrade to a modern web browser.</div>
    </div>
    <div style='width: 75px; float: left;'><a href='http://www.firefox.com' target='_blank'><img src='http://www.ie6nomore.com/files/theme/ie6nomore-firefox.jpg' style='border: none;' alt='Get Firefox 3.5'/></a></div>
    <div style='width: 75px; float: left;'><a href='http://www.browserforthebetter.com/download.html' target='_blank'><img src='http://www.ie6nomore.com/files/theme/ie6nomore-ie8.jpg' style='border: none;' alt='Get Internet Explorer 8'/></a></div>
    <div style='width: 73px; float: left;'><a href='http://www.apple.com/safari/download/' target='_blank'><img src='http://www.ie6nomore.com/files/theme/ie6nomore-safari.jpg' style='border: none;' alt='Get Safari 4'/></a></div>
    <div style='float: left;'><a href='http://www.google.com/chrome' target='_blank'><img src='http://www.ie6nomore.com/files/theme/ie6nomore-chrome.jpg' style='border: none;' alt='Get Google Chrome'/></a></div>
  </div>
</div>
<![endif]-->

How does this work? Why does this show on IE6 but not on newer browsers?

Answer 1

Because of this:

<!--[if lt IE 7]>
...
<![endif]-->

This is a tag recognized only by IE-type browsers, that in English says "if browser version is less than IE7, show this".

Answer 2

Conditional Comments

...it's an IE specific feature that allows you to target different versions of their browsers.

Answer 3

This code "asks" the browser which version it is (using the browser's user agent). If it is "less than" (lt) IE 7 (so IE 6, IE 5, IE 4, IE 3, IE 2, IE 1), then it displays the HTML between the two tags.