When I try to validate my pages containing Flash content, or Quicktime or whatever, I get the message "The tag name 'embed' not found in currently active versions". I get this when using HTML 4.01 or XHTML 1.0 , loose, transitional, or whatever. Do I assume from this that embedding any sort of the aforementioned media types is considered invalid markup? Or is there a way to do it? I've tried looking on W3c.org but not really found anything. It's not a big deal but would be nice to find out.