How to handle meta elements not validating in HTML5?

Question

In HTML5, some meta elements do not validate (yet?) like:

<meta http-equiv="x-ua-compatible" content="ie=emulateie7;chrome=1">
<meta http-equiv="imagetoolbar" content="no">

Are Conditional Comments an appropriate solution here resp. will meta elements still work as expected?

<!--[if IE]><meta http-equiv="x-ua-compatible" content="ie=emulateie7;chrome=1"><![endif]-->
<!--[if lt IE 7]><meta http-equiv="imagetoolbar" content="no"><![endif]-->

Using a .htaccess file instead of meta elements (not always possible unfortunately), would this be the right way to go?

<IfModule mod_setenvif.c>
  <IfModule mod_headers.c>
  # BrowserMatch MSIE ie OR?
    BrowserMatch MSIE emulate_ie7
  # Header set X-UA-Compatible "IE=EmulateIE7" env=ie OR?
    Header set X-UA-Compatible "IE=EmulateIE7" env=emulate_ie7
    BrowserMatch chromeframe gcf
    Header append X-UA-Compatible "chrome=1" env=gcf
  </IfModule>
</IfModule>

Thanks!

Answer 1

Personally for the "x-ua-compatible" tag, i went for the .htaccess directive. I followed the html5boilerplate template:

# ----------------------------------------------------------------------
# Better website experience for IE users
# ----------------------------------------------------------------------

# Force the latest IE version, in various cases when it may fall back to IE7 mode
#  github.com/rails/rails/commit/123eb25#commitcomment-118920
# Use ChromeFrame if it's installed for a better experience for the poor IE folk

<IfModule mod_setenvif.c>
  <IfModule mod_headers.c>
    BrowserMatch MSIE ie
    Header set X-UA-Compatible "IE=Edge,chrome=1" env=ie
  </IfModule>
</IfModule>

<IfModule mod_headers.c>
# Because X-UA-Compatible isn't sent to non-IE (to save header bytes),
#   We need to inform proxies that content changes based on UA
  Header append Vary User-Agent
# Cache control is set only if mod_headers is enabled, so that's unncessary to declare
</IfModule>