It is common that users collect desired information by search engines. Nevertheless, when a user is unfamiliar with his or her search target, some efforts are required to browse and to understand the web pages contained in the corresponding search result. In such an informational web search, it is noted that information cues are cumulated as the user reads more and more web pages to approach the search target. For example, the term "cloud computing" can be gradually understood after the user obtains some information of relevant topics, e.g., distributed computing, Google App Engine, Amazon EC2. In this work, an indicator, i.e., immediacy of interest, is proposed to evaluate the possible user interest toward a web page contained in the search result. Moreover, to address the relevance among search sessions, the topic map is also utilized in our proposed scheme. Empirical studies show that tasks of informational web search can be completed efficiently and effectively with our approach.