The Piwik community doesn’t seem to have much mention of this, other than one mailing list thread. I modified the script to something similar to the one in that thread, like this:
As mentioned in a previous post, my site has gone to the HTML 5 doctype. I had come from XHTML 1.0 and wanted to continue with the XML syntax of HTML 5, but my site wouldn’t validate with the XML declaration. I recently remembered that I had been serving my site with the mime-type “text/html”, which is allowed in XHTML 1.0 . HTML 5 got stricter, and if you want to use the XML syntax, it must be served as “application/xhtml+xml” or “application/xml”.
So I modified the doctype switcher I had made (mentioned in that previous post) to change the mime-type to “application/xhtml+xml” when the configuration doctype was set to “xhtml5”. But IE evidently cannot handle that mime-type, so I set up my switcher to output as “html5” for IE, but “xhtml5” for other browsers. I reset the doctype variable (now an attribute of a page object):