An apparatus and a method perform search operations on a document having nested elements of varying types. The apparatus finds in the document an element which is capable of containing nested elements of one or more varying types. The apparatus can also replace the found element with a substitute element, which is also capable of containing nested elements of one or more varying types. The types of elements include texts, images, animation, and sound clips. For each element, a matching function and a find function are provided. The matching function associated with one element determines if a target element matches itself based on predetermined search criteria. The find function associated with one element searches for a match of a target element within itself. The find function of one element can in turn invoke find functions associated with elements embedded within itself in carrying out the search on the target element.