1. A method of validating a widget on a Web page, comprising: identifying features of a widget of interest on a first Web page, the first Web page capable of including a plurality of independent widgets; generating a widget tree containing a hierarchy of context nodes and feature nodes, each of the context nodes and feature nodes corresponding to one of the features of interest for the identified widget, the widget tree further corresponding to a subset of a first page tree structure for the first Web page; attaching the context nodes of the widget tree to nodes of the first page tree structure; performing a first feature extraction to obtain a first property value for each feature of interest corresponding to a context node or feature node in the widget tree, each first property value being a feature value or context node presence information; and generating a first property vector including each first property value for the widget; detaching the context nodes from the first page tree structure; unloading the first Web page; loading a second Web page containing the widget of interest; attaching the context nodes of the widget tree to nodes of a second page tree structure for the second Web page; performing a second feature extraction to obtain second property values for each feature of interest corresponding to a context node or feature node in the widget tree; generating a second property vector including each second property value for the widget of interest; and comparing the first and second property vectors, wherein a functionality of the widget is validated if the first property vector matches the second property vector.