Steps to reproduce:

1. Prepare an eZ Publish 4.7 installation with all available service packs;
2. Install eZ Find 2.7 and activate autocomplete in ezfind.ini;
3. Enable browser's JS console;
4. Log in to backend siteaccess and go to an user's full view page. Used /Users/Administrator-users/Nuno-Oliveira.

Chrome will display this error:

Uncaught ReferenceError: YAHOO is not defined							ezajax_autocomplete.js:14
	eZAJAXAutoComplete									ezajax_autocomplete.js:14
	(anonymous function)

Whereas FF will display:

ReferenceError: YAHOO is not defined								ezajax_...lete.js (line 14, col 8)
	loader = new YAHOO.util.YUILoader( YUI2_config );