A browser dependent message, explaining the risks of using IE6 and providing download links to a recent browsers.
The warning message will show on on the top of your website, just before the website's header
It will not cover any part of your website, since it will push it a few pixels down to accomodate the warning
No it doesn't use any script, it only uses conditional CSS to display the warning message
The code is w3C valid and passes W3C automatic Validation for XHTML 1.0 Transitional