Here's the deal: somewhere after the introduction of ResourceLoader and the new MediaWiki javascript library, Internet Explorer 6 suffers an inordinate ammount of JavaScript abortion problems. Especially calls to mediawiki.util.js, which are responsible for either "mw.util.[function] is null or not defined" or "Object expected" errors.
The problem became apparent (on en.wiki) after several wikibits functions in Common.jss were changed to use mw.util.* instead. The problem also occurs on Commons and nl.wiki. The *only* way to have a page load correctly, is to issue a hard-reload (using CTRL-F5); only then are all scripts completed. Otherwise, either by using a normal reload or a page-click, all scripts are aborted (even fixalpha and other core scripts).
This has to be an initialization problem, and the casue may lay anywhere, either in the ResourceLoader or the mw.* library, or somewhere else; I have no way to be sure. This *may* also be caused by bug:28840, who knows...
Now, as I have no personal interest in IE6 anymore, and the browser is 10 years old, I am posing the question: is MediaWiki and its JS libraries still officially supporting IE6? If so, then this bug should be traced and fixed. If not, IE6 should be removed from the supported browsers list.
Version: 1.17.x
Severity: critical