This paper presents a JSON based rule language and its JavaScript-based rule engine towards providing Web 2.0 applications with rule-based inference capabilities. For interoperability purposes the Rule Interchange Format is used. While the rule engine is enough general, its main purpose is to execute production rules and Event-ConditionAction rules related to the web page DOM processing. This way the user's browsing experience will be enriched with the ability to modify on the fly the DOM of the current document as well as the browser user interface (Firefox).