Every browser I've observed creates a <head> element that's accessible in the DOM even if there are no explicit <head></head> tags in the document's markup.
However, Google Analytics uses the following code for dynamic script insertion:
(function() {
var ga = document.createElement('script');
ga.type = 'text/javascript';
ga.async = true;
ga.src = ('https:' == document.location.protocol ? 'https://ssl' : 'http://www') + '.google-analytics.com/ga.js';
(document.getElementsByTagName('head')[0] || document.getElementsByTagName('body')[0]).appendChild(ga);
})();
The following line:
(document.getElementsByTagName('head')[0] || document.getElementsByTagName('body')[0]).appendChild(ga);
seems to make a special concession for cases where a <head> element is not present.
Is this just a case of extreme backwards-compatibility (e.g., for Netscape 4, or the like), or is there a case to be made for not assuming that modern browsers (i.e., Internet Explorer 6 and more recent) will always have access to a <head> element in the DOM?