In QueryBuilder.prototype.createRuleInput, the call to $valueContainer.show() sometimes gives the initial rule value container display:block, when it is supposed to have display:inline-block. jQuery gives it display:block if it does not have an initial display attribute. I have not been able to track down why this happens in my app and not in any JSFiddle I have tried, but it's fixed when I replace $valueContainer.css("display", "inline-block") with $valueContainer.show(). Isn't that more reliable anyway?